[compiler-rt] [Fuchsia][cmake] Avoid referencing cxx_shared in compiler-rt (PR #112257)

[Louis Dionne via llvm-commits]

ldionne wrote:

Thanks for the explanation!

> That's correct, we build builtins separately by using https://github.com/llvm/llvm-project/tree/main/compiler-rt/lib/builtins as the top-level CMake build directory

Would it make sense to separate this out of `compiler-rt` then? This sounds like a slightly brittle setup dependency-wise.

> libc++ is currently only used by libFuzzer, ORC and XRay plus all unit tests (since it's a dependency of GoogleTest)

Is there a reason why libFuzzer, ORC and XRay need to explicitly mention the just-built libc++? Couldn't they use whatever standard library is provided by the compiler, which in the case of a bootstrapping build would be the just-built libc++? That would be cleaner than having subparts of compiler-rt depending directly on libc++ targets.

> the other runtimes in compiler-rt like sanitizers only depend on libc++abi

Do you know what they depend on libc++abi for?

https://github.com/llvm/llvm-project/pull/112257