OS X: JDK_HOME configuration

/usr/libexec/java_home helps to set the current JDK_HOME.
Actually JDK_HOME should NOT be set where java (/usr/bin/java) is located.
AC_PATH_PROG(JAVAINTERPRETER, $with_java) returns /usr/bin/java.
/usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java.

Change-Id: Ie3166731c1525f5b44414fa4dda642edb9408757
Reviewed-on: https://gerrit.libreoffice.org/9960
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>