[bindings] fix TLS test failure

[bindings] fix TLS test failure

Since cfe commit r237337, '__declspec(thread)' and 'thread_local' have
been the same since MSVC 2015.  i.e. they are both considered to supply
a dynamic TLS kind, not a static TLS kind.

This test originally did not specify which version of MS compatibility
to assume.  As a result, the test was brittle, since changing the
default compatibility version could break the test.

This commit adds a specific version when building up the flags used to
parse the translation unit, and tests both versions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317706 91177308-0d34-0410-b5e6-96231b3b80d8