[Bug libffi/64572] r219477 breaks bootstrap on x86_64 darwin

[howarth at bromo dot med.uc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64572

--- Comment #21 from howarth at bromo dot med.uc.edu ---
One potential issue could be that src/x86/ffitarget.h has changed
FFI_TRAMPOLINE_SIZE from 10 to 12 for X86_DARWIN which is used in darwin.S...

#define RAW_CLOSURE_CIF_OFFSET ((FFI_TRAMPOLINE_SIZE + 3) & ~3)

Reverting this is insufficient to eliminate the 32-bit regressions though.