tools/Makefile: Don't look into $(TARGET_OS), but $(HOST_OS), to inspect availability of loadable module!

The last commit made run.build.step.test_llvm_1 to fail.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120283 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed