RFR: JDK-8029515 Building multiple configurations fails after removal of old build system

[Magnus Ihse Bursie]

Bug: https://bugs.openjdk.java.net/browse/JDK-8029515

When more than one configuration is present, a subset of these can be 
selected using make CONF=x. If this subset contains more than one 
configuration, the build will fail. This is due to a hard-coded 
reference to the old name of the Makefile, which was not properly 
updated when the old build system was removed and the names was changed.

The additional excluded targets is due to the fact how Jprt.gmk is 
included. It should really have been two files, one to be included 
"globally", and one to be included by Main.gmk (with a proper SPEC). 
This means that it's not possible to call JPRT-specific targets to 
multiple configurations. Not that it's likely anyone needs that, though. 
And it has not been working previously either. We plan to address this 
later on, when we remove the global JPRT "bridge" targets.

WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8029515-fix-building-with-multiple-configurations/webrev.01

/Magnus