buildGoModule: be nicer when overrideAttrs clears passthru (#339042)

    # Handle empty vendorHash; avoid

    # error: empty hash requires explicit hash algorithm

    outputHashAlgo = if finalAttrs.vendorHash == "" then "sha256" else null;

  }).overrideAttrs finalAttrs.passthru.overrideModAttrs;

    # in case an overlay clears passthru by accident, don't fail evaluation

  }).overrideAttrs (finalAttrs.passthru.overrideModAttrs or overrideModAttrs);

    nativeBuildInputs = [ go ] ++ nativeBuildInputs;