To builds the apps with MinGW, the CRT0 library must be ignored because
it is ELF specific and we don't need to go through ELF relocations.
We also apply the GNU_EFI_USE_MS_ABI (since we have it), remove the -z
flags, that are invalid in MinGW, and clean up the apps Makefile.
Note that setjump and debughook are excluded from MinGW builds as they
use constructs that are not available there.
Signed-off-by: Pete Batard <pete@akeo.ie>
As explained at https://stackoverflow.com/a/49830956/1069307, 'asm' is a GNU
extension that will produce an error when using a non GNU standard like -std=c11.
With recent commit 9b1e06cd0cc7937ae291a34f1bb5ec1b4568faee having fixed our use
of -std=c11, the MIPS build failed with the error above.
With this sorted, we also re-enable the MIPS gcc build in GitHub Actions.
