driver: -fhardened and -z lazy/-z norelro [PR117739]

driver: -fhardened and -z lazy/-z norelro [PR117739]

As the manual states, using "-fhardened -fstack-protector" will produce
a warning because -fhardened wants to enable -fstack-protector-strong,
but it can't since it's been overriden by the weaker -fstack-protector.

-fhardened also attempts to enable -Wl,-z,relro,-z,now.  By the same
logic as above, "-fhardened -z norelro" or "-fhardened -z lazy" should
produce the same warning.  But we don't detect this combination, so
this patch fixes it.  I also renamed a variable to better reflect its
purpose.

Also don't check warn_hardened in process_command, since it's always
true there.

Also tweak wording in the manual as Jon Wakely suggested on IRC.

	PR driver/117739

gcc/ChangeLog:

	* doc/invoke.texi: Tweak wording for -Whardened.
	* gcc.cc (driver_handle_option): If -z lazy or -z norelro was
	specified, don't enable linker hardening.
	(process_command): Don't check warn_hardened.

gcc/testsuite/ChangeLog:

	* c-c++-common/fhardened-16.c: New test.
	* c-c++-common/fhardened-17.c: New test.
	* c-c++-common/fhardened-18.c: New test.
	* c-c++-common/fhardened-19.c: New test.
	* c-c++-common/fhardened-20.c: New test.
	* c-c++-common/fhardened-21.c: New test.

Reviewed-by: Jakub Jelinek <jakub@redhat.com>