[runtimes] Add the ability to customize the output name of libc++, libc++abi and libunwind

We already had the ability to do that for libc++.dylib, so this only adds
consistency for all the runtime libraries. This should allow working around
difficulties on AIX as described in https://llvm.org/D134221.

Differential Revision: https://reviews.llvm.org/D135669

NOKEYCHECK=True
GitOrigin-RevId: 10378b3db1f16794109af184819be28581f14c3b
2 files changed
tree: a9fc9376a5a43eb34cc7fcd3af199b8a50fa0171
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT