CI: Try relative import path pattern, since full failed.

Something about it using symlinks is causing trouble:

	$ diff -u <(echo -n) <(go list github.com/gopherjs/gopherjs/compiler/natives/src/...)
	warning: ignoring symlink /home/ubuntu/.go_project/src/github.com/gopherjs/gopherjs
	warning: "github.com/gopherjs/gopherjs/compiler/natives/src/..." matched no packages

circle.yml

@@ -17,7 +17,7 @@ test:
     - diff -u <(echo -n) <(gofmt -d .)
     - go tool vet *.go                                                   # Go package in root directory.
     - for d in */; do echo $d; done | grep -v tests/ | grep -v third_party/ | xargs go tool vet # All subdirectories except "tests", "third_party".
-    - diff -u <(echo -n) <(go list github.com/gopherjs/gopherjs/compiler/natives/src/...) # All those packages should have // +build js.
+    - diff -u <(echo -n) <(go list ./compiler/natives/src/...) # All those packages should have // +build js.
     - >
       gopherjs test -v --short
       github.com/gopherjs/gopherjs/tests