RFR: JDK-8244757 Introduce SetupTarget in Main.gmk

[Magnus Ihse Bursie]

To be able to support JDK-8244410, we need to have a better way to 
handle dependencies. For this reason, the macro SetupTarget is 
introduced. It will take as input everything that is needed to create a 
top-level target in Main.gmk.

As a positive side-effect, it will finally once again be possible to 
list the dependencies for a rule together with the recipe, fixing a 
shortcoming that has plagues Main.gmk for a long time.

In this patch, I create a trivial version of SetupTarget, and switch 
trivial recipes to use this function. By this, I mean recipes that just 
delegate to another makefile, possible setting a specific target and/or 
make arguments. Specifically, this excludes generated target patterns, 
as for the module phases.

Trivial dependencies are also moved into this function. By this, I mean 
"literal" dependencies. Dependencies that are calculated using variables 
or macros might change if they are moved around in the file, and need a 
more thorough analysis before they can be moved.

My intention is to continue moving targets in Main.gmk into the scope of 
SetupTarget, but to avoid regressions and difficult code reviews, I will 
do this step by step.

Bug: https://bugs.openjdk.java.net/browse/JDK-8244757
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8244757-introduce-SetupTarget/webrev.01

/Magnus