Try to get CI working

.gitlab-ci.yml

@@ -12,6 +12,7 @@ image:                             parity/rust-builder:latest
 
 variables:
   GIT_STRATEGY:                    fetch
+  GIT_SUBMODULE_STRATEGY:          recursive
   CARGO_HOME:                      "/ci-cache/${CI_PROJECT_NAME}/cargo/${CI_JOB_NAME}"
   SCCACHE_DIR:                     "/ci-cache/${CI_PROJECT_NAME}/sccache"
   CI_SERVER_NAME:                  "GitLab CI"

.gitmodules

 [submodule "depend/secp256k1"]
 	path = depend/secp256k1
-	url = git@github.com:bitcoin/secp256k1
+	url = https://github.com/bitcoin/secp256k1