RFR: 8038027: DTDBuilder should be run in headless mode

[David DeHaven]

Please review a simple fix for a cosmetic issue:
https://bugs.openjdk.java.net/browse/JDK-8038027

Proposed fix:
diff --git a/make/Tools.gmk b/make/Tools.gmk
--- a/make/Tools.gmk
+++ b/make/Tools.gmk
@@ -71,6 +71,7 @@
    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) \


Test run showed no change in build results.

Need a sponsor to push, any volunteers?

-DrD-