--- a/jdk/make/common/shared/Platform.gmk	Wed Jul 05 17:11:12 2017 +0200
+++ b/jdk/make/common/shared/Platform.gmk	Tue May 11 14:36:10 2010 -0700
@@ -275,7 +275,12 @@
   endif
   ARCH_FAMILY = $(ARCH)
   # Where is unwanted output to be delivered?
-  DEV_NULL = NUL
+  # MKS uses the special file "NUL", cygwin uses the customary unix file.
+  ifeq ($(USING_CYGWIN),true)
+    DEV_NULL = /dev/null
+  else
+    DEV_NULL = NUL
+  endif
   export DEV_NULL
   # Classpath separator
   CLASSPATH_SEPARATOR = ;