RFR: JDK-8198450 Make jdk.internal.vm.compiler/module-info.java.extra reproducable

[Magnus Ihse Bursie]

The file jdk.internal.vm.compiler/module-info.java.extra is generated on 
build time. On systems with non-sorted output from ls and find, the file 
contents will change and thus not be reproducible.

Fix is to sort file system information before using it.
Bug: https://bugs.openjdk.java.net/browse/JDK-8198450
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8198450-make-compiler-module-info_java_extra-reproducable/webrev.01

/Magnus