RFR: JDK-8217269: jpackage Makefile improvments

[Andy Herrick]

Please review the jpackage fix for bug [1] at [2].

This is a fix for the JDK-8200758-branch branch of the open sandbox 
repository (jpackage).

The webrev includes all the jpackage Makefile Improvements listed in 
[1], other than what is covered by [4], and also includes fix for white 
space errors requested in [3].

[1] https://bugs.openjdk.java.net/browse/JDK-8217269

[2] http://cr.openjdk.java.net/~herrick/8217269/webrev.01/

[3] https://bugs.openjdk.java.net/browse/JDK-8216521

[4] https://bugs.openjdk.java.net/browse/JDK-8217317

/Andy