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
