gitlab: 11.10.8 -> 12.0.3

This is a major version bump but things were generally straightforward
save two wrinkles:

 * it is necessary to ignore collisions in the gitlab bundler
   environment as both `omniauth_oauth2_generic` and
   `apollo_upload_server` provide a `console` executable.

 * grpc had to be patched since its build system expects the `AR`
   environment variable to contain not just the path to `ar` but
   also the `rpc` flags (see the discussion in nixpkgs #63056).

pkgs/applications/version-management/gitlab/gitlab-workhorse/default.nix

@@ -3,13 +3,13 @@
 stdenv.mkDerivation rec {
   name = "gitlab-workhorse-${version}";
 
-  version = "8.5.2";
+  version = "8.7.0";
 
   src = fetchFromGitLab {
     owner = "gitlab-org";
     repo = "gitlab-workhorse";
     rev = "v${version}";
-    sha256 = "0c1wpp81wr4x00pmc2z41xh4vy7yk97fkcg0cdy7gbz2hc5cm296";
+    sha256 = "1zlngc498hnzbxwdjn3ymr0xwrnfgnzzhn9lyf37yfbjl8x28n3z";
   };
 
   buildInputs = [ git go ];