Errors originating in C++ files cause unnecessary diffs whenever the engine is updated
(line number changes, etc.) and would cause CI failures due to different formatting
of the file path on Windows (backslashes, worked around here anyway) and when using
SCU builds (`../scu` insert).
- Fix compilation issues by disabling warnings on release builds. This
also strips warnings from expected result before the comparison to
avoid false mismatches.
- Add a `#debug-only` flag to tests. Must be the first line of the test
script. Those won't run with release builds. Can be used for test
cases that rely on checks only available on debug builds.
