Add a package for rust version 1.76.0.

Pkgsrc changes:
 * Adapt checksums and patches.

Upstream chnages:

Version 1.76.0 (2024-02-08)
==========================

Language
--------
- [Document Rust ABI compatibility between various types]
  (rust-lang/rust#115476)
- [Also: guarantee that char and u32 are ABI-compatible]
  (rust-lang/rust#118032)
- [Warn against ambiguous wide pointer comparisons]
  (rust-lang/rust#117758)

Compiler
--------
- [Lint pinned `#[must_use]` pointers (in particular, `Box<T>`
  where `T` is `#[must_use]`) in `unused_must_use`.]
  (rust-lang/rust#118054)
- [Soundness fix: fix computing the offset of an unsized field in
  a packed struct]
  (rust-lang/rust#118540)
- [Soundness fix: fix dynamic size/align computation logic for
  packed types with dyn Trait tail]
  (rust-lang/rust#118538)
- [Add `$message_type` field to distinguish json diagnostic outputs]
  (rust-lang/rust#115691)
- [Enable Rust to use the EHCont security feature of Windows]
  (rust-lang/rust#118013)
- [Add tier 3 {x86_64,i686}-win7-windows-msvc targets]
  (rust-lang/rust#118150)
- [Add tier 3 aarch64-apple-watchos target]
  (rust-lang/rust#119074)
- [Add tier 3 arm64e-apple-ios & arm64e-apple-darwin targets]
  (rust-lang/rust#115526)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------
- [Add a column number to `dbg!()`]
  (rust-lang/rust#114962)
- [Add `std::hash::{DefaultHasher, RandomState}` exports]
  (rust-lang/rust#115694)
- [Fix rounding issue with exponents in fmt]
  (rust-lang/rust#116301)
- [Add T: ?Sized to `RwLockReadGuard` and `RwLockWriteGuard`'s Debug impls.]
  (rust-lang/rust#117138)
- [Windows: Allow `File::create` to work on hidden files]
  (rust-lang/rust#116438)

Stabilized APIs
---------------
- [`Arc::unwrap_or_clone`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.unwrap_or_clone)
- [`Rc::unwrap_or_clone`]
  (https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.unwrap_or_clone)
- [`Result::inspect`]
  (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.inspect)
- [`Result::inspect_err`]
  (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.inspect_err)
- [`Option::inspect`]
  (https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.inspect)
- [`type_name_of_val`]
  (https://doc.rust-lang.org/stable/std/any/fn.type_name_of_val.html)
- [`std::hash::{DefaultHasher, RandomState}`]
  (https://doc.rust-lang.org/stable/std/hash/index.html#structs)
  These were previously available only through `std::collections::hash_map`.
- [`ptr::{from_ref, from_mut}`]
  (https://doc.rust-lang.org/stable/std/ptr/fn.from_ref.html)
- [`ptr::addr_eq`](https://doc.rust-lang.org/stable/std/ptr/fn.addr_eq.html)

Cargo
-----

See [Cargo release notes]
(https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-176-2024-02-08).

Rustdoc
-------
- [Don't merge cfg and doc(cfg) attributes for re-exports]
  (rust-lang/rust#113091)
- [rustdoc: allow resizing the sidebar / hiding the top bar]
  (rust-lang/rust#115660)
- [rustdoc-search: add support for traits and associated types]
  (rust-lang/rust#116085)
- [rustdoc: Add highlighting for comments in items declaration]
  (rust-lang/rust#117869)

Compatibility Notes
-------------------
- [Add allow-by-default lint for unit bindings]
  (rust-lang/rust#112380)
  This is expected to be upgraded to a warning by default in a future Rust
  release. Some macros emit bindings with type `()` with user-provided spans,
  which means that this lint will warn for user code.
- [Remove x86_64-sun-solaris target.]
  (rust-lang/rust#118091)
- [Remove asmjs-unknown-emscripten target]
  (rust-lang/rust#117338)
- [Report errors in jobserver inherited through environment variables]
  (rust-lang/rust#113730)
  This [may warn](rust-lang/rust#120515)
  on benign problems too.
- [Update the minimum external LLVM to 16.]
  (rust-lang/rust#117947)
- [Improve `print_tts`](rust-lang/rust#114571)
  This change can break some naive manual parsing of token trees
  in proc macro code which expect a particular structure after
  `.to_string()`, rather than just arbitrary Rust code.
- [Make `IMPLIED_BOUNDS_ENTAILMENT` into a hard error from a lint]
  (rust-lang/rust#117984)
- [Vec's allocation behavior was changed when collecting some iterators]
  (rust-lang/rust#110353)
  Allocation behavior is currently not specified, nevertheless
  changes can be surprising.
  See [`impl FromIterator for Vec`]
  (https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#impl-FromIterator%3CT%3E-for-Vec%3CT%3E)
  for more details.
- [Properly reject `default` on free const items]
  (rust-lang/rust#117818)

rust176/DESCR

@@ -0,0 +1,13 @@
+Rust is a systems programming language focused on three goals: safety,
+speed, and concurrency.  It maintains these goals without having a
+garbage collector, making it a useful language for a number of use cases
+other languages aren't good at: embedding in other languages, programs
+with specific space and time requirements, and writing low-level code,
+like device drivers and operating systems.
+
+It improves on current languages targeting this space by having a number
+of compile-time safety checks that produce no runtime overhead, while
+eliminating all data races.  Rust also aims to achieve "zero-cost
+abstractions" even though some of these abstractions feel like those of
+a high-level language.  Even then, Rust still allows precise control
+like a low-level language would.

rust176/HOWTO-BOOTSTRAP

@@ -0,0 +1,85 @@
+How to build a rust bootstrap kit using pkgsrc
+----------------------------------------------
+
+A rust bootstrap kit is simply a pre-compiled binary of rust and
+the rust standard library, and contains the "rust" and "rust-std"
+build results, found in
+
+   work/rustc-<version>/build/dist/
+as
+   rust-<version>-<target>.tar.xz
+and
+   rust-std-<version>-<target>.tar.xz
+
+These result files are produced when the "dist" build target is
+used, ref. BUILD_TARGET.   For a normal native build of the rust
+pkgsrc package, the default BUILD_TARGET is "build", not "dist".
+
+There are two possible ways to produce a bootstrap kit:
+
+1) a native build.  This requires minimum preparation, except
+   possibly for setting rust.BUILD_TARGET to "dist" via e.g.
+   /etc/mk.conf.  Note that on NetBSD, using the "BUILD_TARGET" ==
+   "dist" results in the "rust-cargo-static" option being set, ref.
+   options.mk.  This is so that the resulting bootstrap kits are
+   built with mostly-static linking, reducing the run-time dependencies
+   of the bootstrap kits.
+
+2) a cross-build.  This requires a bit of preparation:
+
+   For each target you want to cross-build rust for, you need
+     - the cross toolchain resulting from "build.sh tools" for
+       the intended target
+     - an OS distribution extracted, including the comp.tgz
+       set so that the target's include files can be used
+     - for 32-bit ports, the "libatomic" package needs to be
+       available.  I'm sure there's a clever and long-winded
+       use of pkg_install which can be used to effect this;
+       I on my hand have always just extracted the tgz file
+       and done the minimal cleanup of the "cruft" files
+       which are part of the package meta-data.
+     - Pick a root directory for the target, e.g. /u/i386.
+       Below this directory place the "tools" containing
+       the cross-compiler in a "tools" sub-directory.
+       Similarly, the extracted OS distribution in the "dest"
+       sub-directory.
+
+   There are two methods available for doing the cross-compile:
+
+   a) Using the "cross.mk" file.  For an i386 build against i586, the
+      following settings should be active:
+
+CROSS_ROOT=            /u/i386
+MAKE_ENV+=             CROSS_ROOT=${CROSS_ROOT}
+GNU_CROSS_TARGET=      i486--netbsdelf
+MAKE_ENV+=             GNU_CROSS_TARGET=${GNU_CROSS_TARGET}
+TARGET=                i586-unknown-netbsd
+SCRIPTS=               ${WRKDIR}/scripts
+CONFIGURE_ARGS+=       --host=${TARGET}
+CONFIGURE_ARGS+=       --target=${TARGET}
+CONFIGURE_ARGS+=       --set=target.${TARGET}.cc=${SCRIPTS}/gcc-wrap
+CONFIGURE_ARGS+=       --set=target.${TARGET}.cxx=${SCRIPTS}/c++-wrap
+CONFIGURE_ARGS+=       --set=target.${TARGET}.linker=${SCRIPTS}/gcc-wrap
+CONFIGURE_ARGS+=       --set=target.${TARGET}.ar=${CROSS_ROOT}/tools/bin/${GNU_CROSS_TARGET}-ar
+
+      Then doing a "make" will cross-build rust, including the LLVM
+      embedded in the rust distribution, ref. the defaulting of that
+      option when TARGET is defined ref. options.mk.
+
+      Note that when TARGET is set, the default build target for
+      the rust makefile becomes "dist", so there's no need to set
+      rust.BUILD_TARGET for cross-builds.
+
+   b) Using the "do-cross.mk" Makefile.  This will attempt to
+      cross-build rust for all the targets listed in the SHORT_TARGETS
+      variable in that file.  Overriding the root directories for
+      the various targets can be done by making your own "local-roots.mk"
+      file, ref. "do-cross.mk".
+
+      This will create a "dist" subdirectory in the rust pkgsrc
+      directory, and the bootstrap kits for each architecture, plus
+      the library source kit will be placed in this directory.
+
+The bootstrap kits can then be placed in /usr/pkgsrc/distfiles, and
+be used by the "next" rust version, where you can use "make makesum"
+to compute the updated checksums for the bootstrap kits.