Add make target for running example tests.

Change-Id: I0d0dfda96b99cefb5ef5c16df4a024de5bf8007e
diff --git a/test/examples.sh b/test/examples.sh
index ac2a18c..7ba9cce 100755
--- a/test/examples.sh
+++ b/test/examples.sh
@@ -24,5 +24,6 @@
 
 for test in ${example_tests}; do
   # Source each test script so that exporting variables can be avoided.
+  VPX_TEST_NAME="$(basename ${test%.*})"
   . "${test}"
 done