RFR: JDK-8244844 javac command line is not re-executable

[Magnus Ihse Bursie]

We've broken our golden rule in SetupJavaCompilation, that all command 
lines should be copy/paste:able to re-execute them from the command 
line. The reason is that the file containing the source code file names 
has a temporary name, which is renamed after the compilation. This is 
just a messy way to use the file both as input to javac and as a marker 
that the compilation has succeeded. By splitting up these two roles, we 
get more readable code and a re-executable command line.

Bug: https://bugs.openjdk.java.net/browse/JDK-8244844
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8244844-make-javac-re-executable/webrev.01

/Magnus