Install libatomic.a in top level library directory so that compiler can find it in search directories.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D104908
cmake-3.16+ for AIX changes the default behavior of building a `SHARED` library which breaks AIX's build of libatomic, i.e., cmake-3.16+ builds `SHARED` as an archive of dynamic libraries. To fix it, we have to build `libatomic.so.1` as `MODULE` which keeps `libatomic.so.1` as an normal dynamic library.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D103786
On AIX, we have to ship `libatomic.a` for compatibility. First, a new `clang_rt.atomic` is added. Second, use added cmake modules for AIX, we are able to build a compatible libatomic.a for AIX. The second step can't be perfectly implemented with cmake now since AIX's archive approach is kinda unique, i.e., archiving shared libraries into a static archive file.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D102155
Kai Luo