tests: Add an initial weston integration test

The idea here is to make weston load test cases as a module and then
run test cases from within weston.
diff --git a/tests/weston-test b/tests/weston-test
new file mode 100644
index 0000000..2314514
--- /dev/null
+++ b/tests/weston-test
@@ -0,0 +1,4 @@
+#!/bin/sh
+
+../src/weston --module=$abs_builddir/.libs/${1/.la/.so}
+