Add compile time test to c2hal

This new build rule verifies that c2hal can convert simple.h to
a valid .hal format by generating the C++ files and compiling
the ISimple's shared library.

Test: "make c2hal_test" and verify output
Bug: 32608667
Change-Id: I51021e1441c88cae08872c3fdc81642705c8e17e
diff --git a/c2hal/Android.bp b/c2hal/Android.bp
index f901d24..a634ed6 100644
--- a/c2hal/Android.bp
+++ b/c2hal/Android.bp
@@ -12,6 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+subdirs = [
+    "test",
+]
+
+
 cc_binary_host {
     name: "c2hal",
     srcs: [