hg: panama/panama/scratch: Use correct make variable for clang include dir

[mikael.vidstedt at oracle.com]

Changeset: abe24ccddab9
Author:    mikael
Date:      2016-06-13 16:57 -0700
URL:       http://hg.openjdk.java.net/panama/panama/scratch/rev/abe24ccddab9

Use correct make variable for clang include dir

! jdk.internal.nicl.testgen/make/Tests.gmk