Don't strip -g from RPM_OPT_FLAGS

Missing -g trips over debuginfo generation after latest rpm changes
(only on s390x though, for reasons unknown):

error: Empty %files file /builddir/build/BUILD/libreoffice-5.4.0.3/debugsourcefiles.list

libreoffice.spec

@@ -992,7 +992,7 @@ export PATH=$QT4DIR/bin:$PATH
 #use the RPM_OPT_FLAGS but remove the OOo overridden ones
 for i in $RPM_OPT_FLAGS; do
         case "$i" in
-                -pipe|-Wall|-Werror*|-g|-fexceptions) continue;;
+                -pipe|-Wall|-Werror*|-fexceptions) continue;;
         esac
         ARCH_FLAGS="$ARCH_FLAGS $i"
 done