spirv: Add skip_os_break_in_debug_build option to use in unit tests

spirv: Add skip_os_break_in_debug_build option to use in unit tests

When running in the CI environment, instead of crashing the test
binary, it is preferable to just fail gracefully (in this case return
a NULL shader) like is done in release mode, so other tests continue
to be executed.

For convenience add a variable break_on_failure to the test so the
breaking behavior can be re-enable in individual tests when debugging.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21512>