qt5-build.eclass: disable reduce-relocations

For Qt 5, it's best to just disable reduce-relocations, because it
doesn't (unlike Qt 6) support -mno-direct-extern-access, which means
CMake applications building against Qt 5 are prone to all the issues
mentioned in the bug.

Bug: https://bugs.gentoo.org/754021
Signed-off-by: Sam James <sam@gentoo.org>

eclass/qt5-build.eclass

@@ -1,4 +1,4 @@
-# Copyright 1999-2024 Gentoo Authors
+# Copyright 1999-2025 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: qt5-build.eclass
@@ -679,10 +679,10 @@ qt5_base_configure() {
 		# link-time code generation is not something we want to enable by default
 		-no-ltcg
 
-		# reduced relocations cause major breakage on at least arm and ppc, so
-		# don't specify anything and let the configure figure out if they are
-		# supported; see also https://bugreports.qt.io/browse/QTBUG-36129
-		#-reduce-relocations
+		# Qt 5 doesn't support -mno-direct-extern-access, so uses
+		# -Bsymbolic, which causes issues for consumers if not linking
+		# corectly (bug #754021).
+		-no-reduce-relocations
 
 		# use the system linker (gold will be selected automagically otherwise)
 		$(tc-ld-is-gold && echo -use-gold-linker || echo -no-use-gold-linker)