Merge pull request #237594 from ncfavier/runCommand-position

runCommand: set meta.position from the arguments

pkgs/build-support/trivial-builders/default.nix

@@ -87,6 +87,10 @@ rec {
       inherit buildCommand name;
       passAsFile = [ "buildCommand" ]
         ++ (derivationArgs.passAsFile or []);
+      pos = let args = builtins.attrNames derivationArgs; in
+        if builtins.length args > 0
+        then builtins.unsafeGetAttrPos (builtins.head args) derivationArgs
+        else null;
     }
     // (lib.optionalAttrs runLocal {
           preferLocalBuild = true;