Add libgo dependency on libbacktrace.

Noticed missing dependency when regenerated Makefile.in for unrelated
change with 'autogen Makefile.def'.

The change was lost in r12-6861-gaeac414923aa1e ("Revert "Fix PR 67102:
Add libstdc++ dependancy to libffi" [PR67102]").

/
	* Makefile.in: Regenerate.