aidl: Stop using Bionic's test main

This allows us to build unittests on Mac, where Bionic's test main
does not build.

Change-Id: I59c805d233498bb67575f2e5f7049341f70ce55c
diff --git a/tools/aidl/test_main.cpp b/tools/aidl/test_main.cpp
new file mode 100644
index 0000000..4d820af7
--- /dev/null
+++ b/tools/aidl/test_main.cpp
@@ -0,0 +1,6 @@
+#include <gtest/gtest.h>
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}