Make the debug build compile with -Og
    
    Due to Python's handling of CFLAGS and the way we
    were passing extra compiler flags through the SPEC
    the -Og flag for the debug build was overridden by
    the -O2 flag, resulting in various side effects.
    
    See: https://bugs.python.org/issue37631
    
    Resolves: rhbz#1678277