To apply this patch to the base system, do the following:
cd /usr/src/contrib/
ln -s gdb gdb-4.18
patch -p -E < gdb-4.18-objc-unoff-000325.patch
rm gdb-4.18
cd /usr/src/gnu/usr.bin/binutils/gdb/
Add at the end of the Makefile XSRCS section: objc-lang.c objc-exp.y