Please review changes for JDK-8014762: Add JMC configure option mapping to Jprt.gmk

[Klara Ward]

Need to add the mapping between JPRT env var and configure flag for JMC,
from ALT_JMC_ZIP_DIR to --with-jmc-zip-dir
(same pattern as for Javafx)

http://javaweb.us.oracle.com/~klward/webrev/make_jprt_jdk8/

Thanks,
Klara