[clang] [libcxx] [llvm] Plumb LIBCXX_INSTALL_LIBRARY_PATH through to Clang (#109895) (PR #176772)

[Louis Dionne via cfe-commits]

https://github.com/ldionne requested changes to this pull request.

I think I understand the issue this patch is trying to solve, but hardcoding the path to libc++ in the driver doesn't seem like the right approach to me at the moment. Indeed, the path to libc++ is not something that we know at the time of configuring Clang. There may also be multiple builds of libc++ (one for each target) for a single build of Clang (which is naturally a cross-compiler able to handle many targets). So it seems like there is an impedance mismatch between the information we're trying to share with libc++'s build and the information that we actually need in the driver.

CC @petrhosek 

https://github.com/llvm/llvm-project/pull/176772