Move android nightly build to taskcluster.

etc/taskcluster/decisionlib.py

@@ -173,6 +173,22 @@ class Task:
         self.treeherder_required = False  # Taken care of
         return self
 
+    def with_s3_upload_secret(self):
+        return (
+            self
+            .with_scopes("secrets:get:project/servo/s3-upload")
+            .with_env(PY=r"""if 1:
+                import urllib, json
+                url = "http://taskcluster/secrets/v1/secret/project/servo/s3-upload"
+                secret = json.load(urllib.urlopen(url))["secret"]
+                open("/root/.aws/credentials", "w").write(secret["credentials_file"])
+            """)
+            .with_script("""
+                mkdir /root/.aws
+                python -c "$PY"
+            """)
+        )
+
     def build_worker_payload(self):  # pragma: no cover
         """
         Overridden by sub-classes to return a dictionary in a worker-specific format,