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

[David DeHaven]

Ping? Can a build-dev Reviewer approve this?

-DrD-

>> 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-
>> 
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