fetchgx: fetch dependencies with gx and gx-go

pkgs/build-support/fetchgx/default.nix

@@ -0,0 +1,30 @@
+{ stdenv, gx, gx-go, go, cacert }:
+
+{ name, src, sha256 }:
+
+stdenv.mkDerivation {
+  name = "${name}-gxdeps";
+  inherit src;
+
+  buildInputs = [ go gx gx-go ];
+
+  outputHashAlgo = "sha256";
+  outputHashMode = "recursive";
+  outputHash = sha256;
+
+  phases = [ "unpackPhase" "buildPhase" "installPhase" ];
+
+  SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
+
+  buildPhase = ''
+    export GOPATH=$(pwd)/vendor
+    mkdir vendor
+    gx install
+  '';
+
+  installPhase = ''
+    mv vendor $out
+  '';
+
+  preferLocalBuild = true;
+}

pkgs/top-level/all-packages.nix

@@ -250,6 +250,8 @@ in
   fetchNuGet = callPackage ../build-support/fetchnuget { };
   buildDotnetPackage = callPackage ../build-support/build-dotnet-package { };
 
+  fetchgx = callPackage ../build-support/fetchgx { };
+
   resolveMirrorURLs = {url}: fetchurl {
     showURLs = true;
     inherit url;