The --nofallback option can be used to ensure that the
compiler is not inadvertently executed with optimizations below the that specified by the
-O option.
For example, if an apparently unlicensed compiler was requested to run with level 2 optimizations, it would normally revert to a lower optimization level. With this option, the compiler will instead issue an error and compilation will terminate. Thus, this option can ensure that build are performed with a properly licensed compiler.