do not filter -O? from RPM_OPT_FLAGS:

jakub discovered that LO libraries are built without optimization,
which is because in CWS gnumake4, and thus LO 3.5, the variables
CFLAGS/CXXFLAGS override the optimization and debug settings used by
gbuild, and these are exported by the spec file.

libreoffice.spec

@@ -1026,7 +1026,7 @@ 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
-                -O?|-pipe|-Wall|-g|-fexceptions) continue;;
+                -pipe|-Wall|-g|-fexceptions) continue;;
         esac
         ARCH_FLAGS="$ARCH_FLAGS $i"
 done