Slight fix to generation of SPI files during repeated builds.

buildScripts/compile.ant.xml

@@ -63,6 +63,7 @@ lombok code including the various agents.
 		     and partly because our injection mechanism (annotations) doesn't work very
 		     well on javac 1.5, hence, when using javac, we do demand you're on 1.6. -->
 		<javac includeDestClasses="false" debug="on" destdir="build/lombok" target="1.5">
+			<compilerarg value="-implicit:class" />
 			<src path="src" />
 			<src path="src_eclipseagent" />
 			<exclude name="lombok/javac/**" />
@@ -70,6 +71,7 @@ lombok code including the various agents.
 			<classpath refid="libs.path" />
 		</javac>
 		<javac includeDestClasses="false" srcdir="src" debug="on" destdir="build/lombok" target="1.6" includes="lombok/javac/**">
+			<compilerarg value="-implicit:class" />
 			<classpath refid="deps.path" />
 			<classpath refid="libs.path" />
 		</javac>