Fix makefile and re-enable test disabled due to llvm.org/pr15256
- fix is: don't pass incompatible -stdlib option when building with GCC



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@176460 91177308-0d34-0410-b5e6-96231b3b80d8
Un-skipping tests affected by llvm.org/pr15256

patch by Ashok Thirumurthi!



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@176462 91177308-0d34-0410-b5e6-96231b3b80d8