The original fix for b/139528538 didn't differentiate between release
and debug builds properly. It just just checked to see if a debugger was
attached.

Now the assert will only happen when a debugger is attached and in a
debug build.

Bug: b/159733084
Change-Id: I9a6407685225c662aeb378be3296b8e4640b279d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/46028
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Sean Risser <srisser@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>