Remove obsolete support for linking unwinder on Android

[pcc]

Linking libgcc is no longer supported (see #103673), so remove the related link attributes and the check in unwind's build.rs. The check was the last remaining significant piece of logic in build.rs, so remove build.rs as well.

[rustbot]

r? @Mark-Simulacrum

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[pcc]

cc @chriswailes

[bjorn3]

Somewhat related, but I think libunwind can be removed from

rust/src/bootstrap/src/core/build_steps/dist.rs

Line 912 in c5afe0a

&["library", "src/llvm-project/libunwind"],

as libunwind isn't built from source anymore by the build script of the unwind crate.

[pcc]

Does that mean that we never build libunwind from source? This seems to indicate that we do so by default when targeting Fuchsia:

rust/config.example.toml

Line 760 in c5afe0a

#llvm-libunwind = 'no' if Linux, 'in-tree' if Fuchsia

and the code implementing that is:

rust/src/bootstrap/src/core/config/config.rs

Line 1995 in c5afe0a

LlvmLibunwind::InTree

[bjorn3]

My understanding is that any in-tree building is done by bootstrap. As such the source for libunwind only needs to be in the full source tarball and not the tarball for the standard library source which is never used with bootstrap.

[klensy]

So, drop this too?

rust/library/unwind/Cargo.toml

Lines 22 to 23 in b20f40d

	[build-dependencies]
	cc = "1.0.76"

[rustbot]

Some changes occurred in src/tools/cargo

cc @ehuss

[pcc]

So, drop this too?

rust/library/unwind/Cargo.toml

Lines 22 to 23 in b20f40d

	[build-dependencies]
	cc = "1.0.76"

Done

[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[Mark-Simulacrum]

@bors r+

[bors]

📌 Commit 654288b has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit 654288b with merge 513a485...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 513a485 to master...

[rust-timer]

Finished benchmarking commit (513a485): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.3%, 0.3%]	1

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.9%	[0.6%, 4.3%]	3
Regressions ❌ (secondary)	2.3%	[0.7%, 3.9%]	2
Improvements ✅ (primary)	-1.2%	[-1.4%, -0.9%]	2
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	0.7%	[-1.4%, 4.3%]	5

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.6%, -0.4%]	3
Improvements ✅ (secondary)	-0.6%	[-0.6%, -0.6%]	1
All ❌✅ (primary)	-0.5%	[-0.6%, -0.4%]	3

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 639.017s -> 637.364s (-0.26%)
Artifact size: 304.51 MiB -> 304.54 MiB (0.01%)