My case:
1. Project, used on different PC with different compiler:
<Option compiler="nixman_131_ucrt_win32_gnu_gcc_64" />
was opened in C::B.
2. It proposed me to change non-existing compiler with incorrect one.
3. I choose correct.
4. I applied changes on all targets.
Everything looks fine at that moment, but options_gcc.xml was generated. When I opened C::B next time, I got empty compiler flags.