build: dont detect libraries for Windows

Hard code the defaults for Windows for the time being.  The checks
really are always going to return the same value.  Technically, the
pthread linkage is possible, however, it seems better to use the Win32
threading along with the external threading support that we have added.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@290801 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed