When running configure, you can override any tool location by setting
the variable name on the command line (e.g. configure
MAKE=/path/to/make). Configure also includes validation that any such
argument actually corresponds to a valid variable and will print a
warning if no match is found.
This validation logic is currently evaluated before the CUSTOM_LATE_HOOK
is called so any variable defined there will still trigger the warning
if specified on the command line. This patch moves the validation to
after CUSTOM_LATE_HOOK.
Bug: https://bugs.openjdk.java.net/browse/JDK-8196365
Webrev: http://cr.openjdk.java.net/~erikj/8196365/webrev.01/index.html
/Erik
