Conditionally export `libprofiler_builtins` from `rust_library` CcInfo

[StephanDollberg]

Is your feature request related to a problem? Please describe.

A C++ executable built with Clang PGO can depend on an uninstrumented
rust_library. Today that Rust target unconditionally propagates the Rust
toolchain's libprofiler_builtins through CcInfo. The archive can appear
before Clang's driver-provided libclang_rt.profile.a and satisfy the same
__llvm_profile_* symbols first.

If rustc and Clang use different LLVM profile ABIs, the resulting executable
links successfully but uses a runtime that cannot interpret the C++
instrumentation data and very likely crashes on startup.

Our concrete configuration is:

• rules_rust 0.70.0; current upstream has the same propagation behavior
• Rust 1.91.0 using LLVM 21.1.2
• Clang 23
• C++ compiled with -fprofile-generate
• Rust dependencies intentionally not PGO-instrumented

rust_stdlib_filegroup places libprofiler_builtins-*.rlib in
between_core_and_std_files. make_libstd_and_allocator_ccinfo exports every
archive in that collection, and establish_cc_info attaches the resulting
standard-library CcInfo to rust_library targets.

The final link is effectively ordered as follows:

libprofiler_builtins-<hash>.rlib
...
-u__llvm_profile_runtime
libclang_rt.profile.a

Because static archives are extracted lazily, Rust's LLVM 21 runtime satisfies
the profile symbols and Clang 23's runtime is not extracted.

This issue has already been described in other semi-related issues like: #1324 (comment)

Describe the solution you'd like

An uninstrumented rust_library should not export libprofiler_builtins
through CcInfo.

Describe alternatives you've considered
Hacking around on our side.

Additional context