Set up a test for hidden API enforcement

Submitting the test first for easier review. The expected outcome
is that all currently class members are discoverable and accessible.
Future CLs will implement the enforcement and change the expected
outcome.

The test itself has two JARs - parent declares classes and child
tries to access them using reflection, JNI and static linking.
The test driver ("Main" class) loads these JARs as follows:
(a) both with class loaders
(b) parent in boot class path, child with class loader
(c) both in boot class path

In (a), there should be no enforcement as the JAR does not have
hidden API access flags (would not load otherwise). In situation(b),
child should only be allowed to access parent's public, non-hidden
members. And in (c), parent contains hidden API access flags but
child is exempt from access checks.

Bug: 64382372
Test: art/test.py -b -r -t 674-hiddenapi
Change-Id: I19f5f7c30c0c7913703209817d36006b161c6778
diff --git a/test/run-test b/test/run-test
index 75fe15c..bde3aac 100755
--- a/test/run-test
+++ b/test/run-test
@@ -113,6 +113,11 @@
 fi
 export ZIPALIGN
 
+# If hiddenapi was not set by the environment variable, assume it is in the path.
+if [ -z "$HIDDENAPI" ]; then
+  export HIDDENAPI="hiddenapi"
+fi
+
 info="info.txt"
 build="build"
 run="run"