Enables macros like ASSERT, UNIMPLEMENTED even in release builds.

Bug: b/126329018
Change-Id: I7d810862b16d85b0a4ffc6b39a655cc73d4c669a
Reviewed-on: https://swiftshader-review.googlesource.com/c/25557
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>