Use ENABLE_DEBUG as a better indicator for "debug build"

...than gb_DEBUGLEVEL as had been chosen by
448008d64c "only enable windows incremental
linking for debug builds"

Change-Id: Iabd2904596b3ac2a9d1c55d074cc929572615265
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165077
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>

solenv/gbuild/platform/com_MSC_class.mk

@@ -323,7 +323,7 @@ endef
 gb_Windows_PE_TARGETTYPEFLAGS := \
 	-release \
 	-opt:noref \
-	$(if $(filter 0,$(gb_DEBUGLEVEL)), -incremental:no) \
+	$(if $(ENABLE_DEBUG),, -incremental:no) \
 	$(if $(filter NO,$(LIBRARY_X64)), -safeseh) \
 	-nxcompat \
 	-dynamicbase \