Using make modern on Msys2 and Cygwin makes the build fail with:
data/mystery_gift.s:18: error: include/constants/rematches.h:4: empty enum is invalid
make: *** [Makefile:347: build/modern/data/mystery_gift.o] Error 1
make: *** Deleting file 'build/modern/data/mystery_gift.o'
Good commit: a3d5f54
Bad commit: 3f49c5c
Building with make modern on other systems doesn't fail.