[foreign] RFR 8229122: 4 panama foreign tests fail on Mac OS Mojave

[sundararajan.athijegannathan at oracle.com]

Please review.

4 panama foreign tests fail because /usr/include is missing in Mojave. 
For now, fixing the tests with explicit -I option for SDK header directory.

Bug: https://bugs.openjdk.java.net/browse/JDK-8229122

Webrev: http://cr.openjdk.java.net/~sundar/8229122/webrev.00/

Thanks,

-Sundar