I found the latest version of both master and emacs-30 branch (from Monday) failed to be built on MINGW64 / windows10.
It failed when starting native compilation, error pops up "Cannot find libgccjit library" (from comp-ensure-native-compiler), maybe the called function "load_gccjit_if_necessary / init_gccjit_functions" return error.

But if to revert the change introduced by branch "savannah/scratch/windows-98" (merged on 2024/06/30), the build becomes OK.
git revert 38179f85f8f7236d5de8d9a4333b6a1d4ded63f0
So that maybe the issue is caused by the 3 commits in this branch.