[Bug libgcc/123976] GCC 15.2.0 (libgcc) does not build on PPC Mac OS X 10.5.8, Leopard, because of missing "md-unwind-def.h"

[vital.had at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123976

--- Comment #107 from Sergey Fedorov <vital.had at gmail dot com> ---
This is needed too:
https://github.com/iains/gcc-16-branch/commit/1aabd474c7f58e069e49b6096056937389ba7b51

It is identical to what gcc16 port has:
https://github.com/macos-powerpc/powerpc-ports/blob/f24237268895c848d177748ca88861dcde53c4f0/lang/gcc16/files/patch-libstdcxx-call_once.patch

But Iain may have an updated version of it now.