[ASan] don't use -m{32,64} flag in test case, as it can be run in both 32- and 64-bit modes

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@183638 91177308-0d34-0410-b5e6-96231b3b80d8
[MSan] don't add msan unit tests to check-msan command if libcxx is not checked out

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@183641 91177308-0d34-0410-b5e6-96231b3b80d8