[CMake][runtimes] Use -nodefaultlibs for the runtimes build

We may not have a working C++ standard library at this point so we
shouldn't rely on it when running CMake checks.

Differential Revision: https://reviews.llvm.org/D31942

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300260 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed