Fix: work around GCC compiler bug #105120 in fmt

The fmt code pushes a pragma option, and later pops is. The intrinsics code
interacts with it via the __OPTIMIZE__ macro. This has been set by the pragma
option push, but not unset/reset to the original with the pop.
Since the pragma is only used for the GCC compiler (not Clang, not MSVC, not
ICC) and in debug mode, just remove the whole pragma handling for it.