[8u20] RFR: 8038027: DTDBuilder should be run in headless mode

[David DeHaven]

Please review my trivial backport of JDK-8038027. The actual change is identical to 9, the difference is the surrounding $(JAVA) is $(JAVA_SMALL) in JDK 9.

JBS Issue:
https://bugs.openjdk.java.net/browse/JDK-8038027

JDK 9 changeset:
http://hg.openjdk.java.net/jdk9/dev/jdk/rev/0eab6c63201d

JDK 9 review:
http://mail.openjdk.java.net/pipermail/build-dev/2014-March/012182.html

8u patch:
--- cut here ---
diff --git a/make/Tools.gmk b/make/Tools.gmk
--- a/make/Tools.gmk
+++ b/make/Tools.gmk
@@ -80,6 +80,7 @@
     build.tools.generatecharacter.CharacterName
 
 TOOL_DTDBUILDER = $(JAVA) -Ddtd_home=$(JDK_TOPDIR)/make/data/dtdbuilder \
+    -Djava.awt.headless=true \
     -cp $(JDK_OUTPUTDIR)/btclasses build.tools.dtdbuilder.DTDBuilder
 
 TOOL_GENERATEBREAKITERATORDATA = $(JAVA) \
--- cut here ---

-DrD-