xorg-3.eclass: strip -fno-plt from *FLAGS

As discussed in #778494, the GCC flag -fno-plt will break lazy
binding, which appears to still be necessary for Xorg. Stripping the
offending flag out is the next best solution for reliable user
experience on Gentoo.

Closes: https://bugs.gentoo.org/778494
Signed-off-by: Niklāvs Koļesņikovs <89q1r14hd@relay.firefox.com>

eclass/xorg-3.eclass

@@ -1,4 +1,4 @@
-# Copyright 1999-2020 Gentoo Authors
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: xorg-3.eclass
@@ -327,7 +327,7 @@ xorg-3_flags_setup() {
 	[[ ${CHOST} == *-winnt* ]] && append-cppflags -DWIN32 -D__STDC__
 	# hardened ldflags
 	[[ ${PN} == xorg-server || ${PN} == xf86-video-* || ${PN} == xf86-input-* ]] \
-		&& append-ldflags -Wl,-z,lazy
+		&& filter-flags -fno-plt && append-ldflags -Wl,-z,lazy
 
 	# Quite few libraries fail on runtime without these:
 	if has static-libs ${IUSE//+}; then