set JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF8 in JavaClassSet.mk

.. to fix reportbuilder build with Java9.
A direct -Dfile.encoding=UTF8 doesn't work...

Change-Id: I231b2893df463d00eb514c0d50e02c8df41c5b20

solenv/gbuild/JavaClassSet.mk

@@ -17,7 +17,8 @@
 #   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 #
 
-gb_JavaClassSet_JAVACCOMMAND := $(ICECREAM_RUN) $(JAVACOMPILER) $(JAVAFLAGS) \
+gb_JavaClassSet_JAVACCOMMAND := JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF8 \
+    $(ICECREAM_RUN) $(JAVACOMPILER) $(JAVAFLAGS) \
     -source $(JAVA_SOURCE_VER) -target $(JAVA_TARGET_VER) \
     $(if $(JAVA_CLASSPATH_NOT_SET),-Xlint:-options)
 gb_JavaClassSet_JAVACDEBUG :=