gawk: ensure cross compiling doesn't try to remove host files

gawk: ensure cross compiling doesn't try to remove host files

Fixes [YOCTO #6440]

When cross compiling gawk, it is possible to see this fail:

make[4]: Entering directory '/mnt/home/paul/poky/build/tmp/work/corei7-64-poky-
linux/gawk/4.1.1-r0/build/extension'
for i in filefuncs.la fnmatch.la fork.la inplace.la ordchr.la readdir.la readfi
le.la revoutput.la revtwoway.la rwarray.la testext.la time.la ; do \
        rm -f /usr/lib/gawk/$i ; \
done
rm: cannot remove '/usr/lib/gawk/filefuncs.la': Permission denied
rm: cannot remove '/usr/lib/gawk/fnmatch.la': Permission denied
rm: cannot remove '/usr/lib/gawk/fork.la': Permission denied
rm: cannot remove '/usr/lib/gawk/inplace.la': Permission denied
rm: cannot remove '/usr/lib/gawk/ordchr.la': Permission denied
rm: cannot remove '/usr/lib/gawk/readdir.la': Permission denied
rm: cannot remove '/usr/lib/gawk/readfile.la': Permission denied
rm: cannot remove '/usr/lib/gawk/revoutput.la': Permission denied
rm: cannot remove '/usr/lib/gawk/revtwoway.la': Permission denied
rm: cannot remove '/usr/lib/gawk/rwarray.la': Permission denied
rm: cannot remove '/usr/lib/gawk/testext.la': Permission denied
rm: cannot remove '/usr/lib/gawk/time.la': Permission denied
Makefile:1235: recipe for target 'install-data-hook' failed

The problem only manifests itself on hosts where the above files
are already present; for if they are absent then the rm -f does
not fail with -EPERM.

Before looking in mainline gawk for a fix, I fixed it myself.
Then in comparing with mainline gawk, I found their fix was
not 100% complete.  So here we get a backport of the mainline
gawk commit, plus the delta as a commit that I've sent to the
gawk mailing list.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>