uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

pkgs/build-support/fetchhg/default.nix

@@ -0,0 +1,29 @@
+{ lib, stdenvNoCC, mercurial }:
+{ name ? null
+, url
+, rev ? null
+, md5 ? null
+, sha256 ? null
+, fetchSubrepos ? false
+, preferLocalBuild ? true }:
+
+if md5 != null then
+  throw "fetchhg does not support md5 anymore, please use sha256"
+else
+# TODO: statically check if mercurial as the https support if the url starts woth https.
+stdenvNoCC.mkDerivation {
+  name = "hg-archive" + (if name != null then "-${name}" else "");
+  builder = ./builder.sh;
+  nativeBuildInputs = [mercurial];
+
+  impureEnvVars = lib.fetchers.proxyImpureEnvVars;
+
+  subrepoClause = if fetchSubrepos then "S" else "";
+
+  outputHashAlgo = "sha256";
+  outputHashMode = "recursive";
+  outputHash = sha256;
+
+  inherit url rev;
+  inherit preferLocalBuild;
+}