go-modules: Add useVend flag to go-modules

pkgs/development/go-modules/generic/default.nix

@@ -1,4 +1,4 @@
-{ go, cacert, git, lib, removeReferencesTo, stdenv }:
+{ go, cacert, git, lib, removeReferencesTo, stdenv, vend }:
 
 { name ? "${args'.pname}-${args'.version}"
 , src
@@ -20,6 +20,9 @@
 , vendorSha256
 # Whether to delete the vendor folder supplied with the source.
 , deleteVendor ? false
+# Whether to run the vend tool to regenerate the vendor directory.
+# This is useful if any dependency contain C files.
+, runVend ? false
 
 , modSha256 ? null
 
@@ -48,6 +51,8 @@ let
 
   deleteFlag = if deleteVendor then "true" else "false";
 
+  vendCommand = if runVend then "${vend}/bin/vend" else "false";
+
   go-modules = if vendorSha256 != null then go.stdenv.mkDerivation (let modArgs = {
 
     name = "${name}-go-modules";
@@ -87,7 +92,13 @@ let
         echo "vendor folder exists, please set 'vendorSha256=null;' or 'deleteVendor=true;' in your expression"
         exit 10
       fi
-      go mod vendor
+
+      if [ ${vendCommand} != "false" ]; then
+        echo running vend to rewrite vendor folder
+        ${vendCommand}
+      else
+        go mod vendor
+      fi
       mkdir -p vendor
 
       runHook postBuild