Include lib/cmake/clang files in clang+llvm tarballs

[MaskRay]

Regarding clang+llvm releases on https://github.com/songdongsheng/asset-store

https://discourse.llvm.org/t/llvm-20-x-release-third-party-binaries/84366/3

Older LLVM releases on releases.llvm.org contain CMake config files for both llvm and clang, e.g.

% ls clang+llvm-14.0.6-x86_64-linux-gnu-rhel-8.4/lib/cmake/clang/
AddClang.cmake  ClangConfig.cmake  ClangTargets-release.cmake  ClangTargets.cmake

This enables projects using CMake find_package(Clang REQUIRED) to locate the Clang library via:

-DCMAKE_PREFIX_PATH=path/to/clang+llvm-14.0.6-x86_64-linux-gnu-rhel-8.4

It would be helpful to include the lib/cmake/clang directory in your tarballs as well to maintain this functionality for downstream projects relying on Clang's API.

In tarballs that target glibc 2.36+, you might specify LDFLAGS -z pack-relative-relocs to utilize the compact relative relocation feature (DT_RELR) to make the executables smaller.

[songdongsheng]

I use LLVM_INSTALL_TOOLCHAIN_ONLY=ON to reduce the package size, so it removes many of the LLVM development and testing tools as well as component libraries from the default install target. Have you tried option pack-relative-relocs to see how much it can reduce the size?