'target'. Latter is problematic in particular as apparently FreeBSD's
bsd.prog.mk re-defines it under some circumstances. This causes an
unexpected failures like -dumpmachine not working for cc while working
fine for c++.
Do not re-define IN_GCC in multipe places, it gets inherited from
Makefile.in anyway.
PR: gnu/110143
Submitted by: usleepless at gmail
cat ${.ALLSRC} > ${.TARGET}
rather than
ln -sf ${.ALLSRC} ${.TARGET}
not to depends on absolute-path of symbolic links.
Commented by: marcel, obrien, bde
