Remove stale Autoconf checks for Perl
Subversion r110220 (Git commit
03b8fe495d716c004f5491eb2347537f115ab2d8) for
PR25884 "libgomp should not require perl to compile" removed all '$(PERL)'
usage from libgomp -- but didn't remove the then-unused Autoconf Perl check
itself. Later, this Autoconf Perl check appears to have been copied from
libgomp into other GCC libraries, likewise unused.
libgomp/
* configure.ac (PERL): Remove.
* configure: Regenerate.
* Makefile.in: Likewise.
* testsuite/Makefile.in: Likewise.
libatomic/
* configure.ac (PERL): Remove.
* configure: Regenerate.
* Makefile.in: Likewise.
* testsuite/Makefile.in: Likewise.
libgm2/
* configure.ac (PERL): Remove.
* configure: Regenerate.
* Makefile.in: Likewise.
* libm2cor/Makefile.in: Likewise.
* libm2iso/Makefile.in: Likewise.
* libm2log/Makefile.in: Likewise.
* libm2min/Makefile.in: Likewise.
* libm2pim/Makefile.in: Likewise.
libitm/
* configure.ac (PERL): Remove.
* configure: Regenerate.
* Makefile.in: Likewise.
* testsuite/Makefile.in: Likewise.