--- a/langtools/make/Makefile	Fri Nov 20 10:15:54 2009 -0800
+++ b/langtools/make/Makefile	Fri Nov 20 11:18:43 2009 -0800
@@ -133,6 +133,23 @@
   ANT_JAVA_HOME = JAVA_HOME=$(ALT_BOOTDIR)
 endif
 
+# To facilitate bootstrapping, much of langtools can be compiled with (just)
+# a boot JDK. However, some source files need to be compiled against 
+# new JDK API. In a bootstrap build, an import JDK may not be available,
+# so build.xml can also build against the source files in a jdk repo,
+# in which case it will automatically generate stub files for the new JDK API.
+ifdef JDK_TOPDIR
+  ANT_OPTIONS += -Dimport.jdk=$(JDK_TOPDIR)
+else 
+  ifdef ALT_JDK_TOPDIR
+    ANT_OPTIONS += -Dimport.jdk=$(ALT_JDK_TOPDIR)
+  else 
+    ifdef ALT_JDK_IMPORT_DIR
+      ANT_OPTIONS += -Dimport.jdk=$(ALT_JDK_IMPORT_DIR)
+    endif
+  endif
+endif
+
 ifdef ALT_OUTPUTDIR
   OUTPUTDIR = $(ALT_OUTPUTDIR)
   ANT_OPTIONS += -Dbuild.dir=$(ALT_OUTPUTDIR)/build