[libc++] Re-apply workaround for D63883

In reality, this workaround is for the fact that LIBCXX_CXX_ABI=libcxxabi
can't be specified on Linux, since libc++abi isn't shipped with the system.
Since the build bots explicitly specify LIBCXX_CXX_ABI=libcxxabi, they fail
unless we apply the workaround.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@373385 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed