librevenge: pass optimization flags to configure

Change-Id: I27220fe91299ccee1e89df1b865dd1de550a01a0
Reviewed-on: https://gerrit.libreoffice.org/43970Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>

external/librevenge/ExternalProject_librevenge.mk

@@ -34,7 +34,8 @@ $(call gb_ExternalProject_get_state_target,librevenge,build) :
 			--disable-generators \
 			--without-docs \
 			$(if $(verbose),--disable-silent-rules,--enable-silent-rules) \
-			CXXFLAGS="$(CXXFLAGS) $(BOOST_CPPFLAGS)" \
+			CXXFLAGS="$(gb_CXXFLAGS) $(if $(ENABLE_OPTIMIZED),$(gb_COMPILEROPTFLAGS),$(gb_COMPILERNOOPTFLAGS))" \
+			CPPFLAGS="$(CPPFLAGS) $(BOOST_CPPFLAGS)" \
 			$(if $(CROSS_COMPILING),--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM)) \
 			$(if $(filter MACOSX,$(OS)),--prefix=/@.__________________________________________________OOO) \
 		&& $(MAKE) \