Bug: https://bugs.openjdk.java.net/browse/JDK-8022411
This is kind of the opposite of JDK-8031669. In that bug, simple tools could be overridden with an absolute path, but not with just an executable in $PATH. This bug is about CC and CXX, which can be overridden with an executable in $PATH, but not with an absolute path.
Webrev: http://cr.openjdk.java.net/~ihse/JDK-8022411-override-CXX-CC-with-absolute-path/webrev.01
/Magnus
