Add ability to optionally skip the build target (which does the compilation)

build.xml

@@ -595,7 +595,7 @@
          Build the code
        ===================================================================
   -->
-  <target name="build" depends="prepare, compile, compile-jdk9+"
+  <target name="build" depends="prepare, compile, compile-jdk9+" unless="skip.build"
           description="--> compiles the source code">
 
     <!-- Builds and verifies that the classes belonging in the confined package of