getdeps: add a test target to eden_scm getdeps manifest

Summary: Add a test target to the eden_scm getdeps manifest and underlying Makefile

Reviewed By: markbt

Differential Revision: D27336805

fbshipit-source-id: 07ec4be1ff03c6a384451ce138d88938dd4bf86e

build/fbcode_builder/manifests/eden_scm

@@ -24,6 +24,9 @@ getdepsbuild
 [make.install_args]
 install-getdeps
 
+[make.test_args]
+test-getdeps
+
 [shipit.pathmap]
 fbcode/eden/oss = .
 fbcode/eden = eden