--- a/make/InitSupport.gmk	Thu Feb 07 10:26:32 2019 +0100
+++ b/make/InitSupport.gmk	Thu Feb 07 12:35:45 2019 +0100
@@ -483,7 +483,7 @@
 	    $(TOUCH) $(SJAVAC_SERVER_DIR)/server.port.stop; true
   endef
 
-  ifeq ($(OPENJDK_BUILD_OS), windows)
+  ifeq ($(call isBuildOs, windows), true)
     # On windows we need to synchronize with the javac server to be able to
     # move or remove the build output directory. Since we have no proper
     # synchronization process, wait for a while and hope it helps. This is only