[ASan/Win tests] Don't generate debug info where it is not needed

Otherwise it results in flaky tests

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@213667 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan/Win tests] Bring back -GS- as SEH tests fail otherwise

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@213668 91177308-0d34-0410-b5e6-96231b3b80d8