qt5-build.eclass: add -no-ltcg for 5.6 and later

(cherry picked from proj/qt commit a72b03f11e9d003e26607a1c80457bbf574fe3d7)

diff --git a/eclass/qt5-build.eclass b/eclass/qt5-build.eclass
index db08161cc87dba943ca7266bc1667e5cab236a03..270ab1302072b32c6338a01ffd7441c380b8876e 100644 (file)
--- a/eclass/qt5-build.eclass
+++ b/eclass/qt5-build.eclass
@@ -583,13 +583,15 @@ qt5_base_configure() {
                -no-icu -no-fontconfig
                -no-dbus
 
-               # don't strip
+               # let portage handle stripping
                -no-strip
 
-               # precompiled headers are not that useful for us
-               # and cause problems on hardened, so turn them off
+               # precompiled headers can cause problems on hardened, so turn them off
                -no-pch
 
+               # link-time code generation is not something we want to enable by default
+               $([[ ${QT5_MINOR_VERSION} -ge 6 ]] && echo -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