+whole-archive link modifier causes build failure on staticlib crate with Rust 1.69

[Be-ing]

Code

I tried this code in a library used in build.rs

        // Static QML plugin and Qt resource initialization need to be linked with +whole-archive
        // because they use static variables which need to be initialized before main
        // (regardless of whether main is in Rust or C++). Normally linkers only copy symbols referenced
        // from within main when static linking, which would result in discarding those static variables.
        // Use a separate cc::Build for the little amount of code that needs to be linked with +whole-archive
        // to avoid bloating the binary.
        let mut cc_builder_whole_archive = cc::Build::new();
        cc_builder_whole_archive.link_lib_modifier("+whole-archive");
        ...
        // cc::Build::file and cc::Build::compile are called on cc_builder_whole_archive later

In Cargo.toml:

[lib]
crate-type = ["staticlib"]

I expected to see this happen: build succeeds, but +whole-archive effectively does nothing because the final link of the executable is done by an external build system (CMake in this case)

Instead, this happened: build fails with

error: link modifiers combination `+bundle,+whole-archive` is unstable when generating rlibs

KDAB/cxx-qt#519

Version it worked on

It most recently worked on: 1.68

Version with regression

1.69.0

Backtrace

N/A

Workaround

Add -bundle link modifier:

cc_builder_whole_archive.link_lib_modifier("-bundle");

KDAB/cxx-qt#520

Neither +bundle nor -bundle seem to make much sense for a staticlib which is built by cc rather than rustc, so adding -bundle doesn't seem to have any downside for CXX-Qt's purposes.

Context

The CXX-Qt build system supports building two ways:

• Rust staticlib crate which gets linked with C++ code built by CMake using CMake's equivalent of +whole-archive: target_link_libraries(${APP_NAME}_lib INTERFACE "$<LINK_LIBRARY:WHOLE_ARCHIVE,${CRATE}-static>")
• Rust bin crate

The Rust bin crate case is still working. The Rust staticlib case fails with the confusing error about rlibs in Rust 1.69. From the Zulip discussion, this seems to be a regression from #105601. This error should be ignored when the crate being built isn't an rlib.