RFR: JDK-8031759 Configure should handle overrides of tools better

Mon Jan 20 14:57:57 UTC 2014

Bug: https://bugs.openjdk.java.net/browse/JDK-8031759

In a way, this is a continuation of JDK-8022411. While that bug fixed 
the ability to properly override CC/CXX with either a complete path, or 
just a command name that was to be searched in $PATH, this fix does the 
same for all other tools that are located, not only the compilers. 
(Boot-JDK tools being the exception; this is issue might be addressed 
soon too.)

With this fix, user overrides will always be honored, and they will 
never fail silently.

I believe this fix supersedes the pending fix for JDK-8031669, which is 
still awaiting approval from a formal reviewer.

WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8031759-better-overriding-of-tools-in-configure/webrev.01

/Magnus