[libcxxabi][libunwind] Support for using LLVM libc (#134893)

This generalizes the support added in #99287 renaming the option to
RUNTIMES_USE_LIBC and integrating the module into libc++abi and
libunwind as well.

NOKEYCHECK=True
GitOrigin-RevId: 9d3b60dea7ad81f6cb0d9f2e51bb6c80c03fa2d4
2 files changed
tree: 1f81b5d6b9c9f219e0a37f112e6724cdeacc0730
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT