This lets us use the SAL annotations to detect locking bugs on MSVC, and are nops on other platforms.

Bug: b/139010488
Change-Id: Ibe63befa9fb88078d2af3e9a9ade71bd21a37090
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34811Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>