sys-libs/glibc: add filter-flags for CET to 2.34-r10 too

May as well add it to the stable one as lots of people seem
to be shoving this in CFLAGS in make.conf now and don't
want more dupes.

See 256df48ff6 for more
background.

Bug: https://bugs.gentoo.org/830454
See: 256df48ff6
Signed-off-by: Sam James <sam@gentoo.org>

sys-libs/glibc/glibc-2.34-r10.ebuild

@@ -440,6 +440,9 @@ setup_flags() {
 	replace-flags -O0 -O1
 
 	filter-flags '-fstack-protector*'
+
+	# See end of bug #830454; we handle this via USE=cet
+	filter-flags '-fcf-protection='
 }
 
 use_multiarch() {