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/tools/nix/npins/source.nix

@@ -0,0 +1,57 @@
+# Not part of the public API – for use within nixpkgs only
+#
+# Usage:
+# ```nix
+# let
+#   sources = builtins.fromJSON (builtins.readFile ./sources.json);
+# in mkMyDerivation rec {
+#   version = src.version; # This obviously only works for releases
+#   src = pkgs.npins.mkSource sources.mySource;
+# }
+# ```
+
+{ fetchgit
+, fetchzip
+, fetchurl
+}:
+let
+  mkSource = spec:
+    assert spec ? type; let
+      path =
+        if spec.type == "Git" then mkGitSource spec
+        else if spec.type == "GitRelease" then mkGitSource spec
+        else if spec.type == "PyPi" then mkPyPiSource spec
+        else if spec.type == "Channel" then mkChannelSource spec
+        else throw "Unknown source type ${spec.type}";
+    in
+    spec // { outPath = path; };
+
+  mkGitSource = { repository, revision, url ? null, hash, ... }:
+    assert repository ? type;
+    # At the moment, either it is a plain git repository (which has an url), or it is a GitHub/GitLab repository
+    # In the latter case, there we will always be an url to the tarball
+    if url != null then
+      (fetchzip {
+        inherit url;
+        sha256 = hash;
+        extension = "tar";
+      })
+    else assert repository.type == "Git"; fetchgit {
+      url = repository.url;
+      rev = revision;
+    };
+
+  mkPyPiSource = { url, hash, ... }:
+    fetchurl {
+      inherit url;
+      sha256 = hash;
+    };
+
+  mkChannelSource = { url, hash, ... }:
+    fetchzip {
+      inherit url;
+      sha256 = hash;
+      extension = "tar";
+    };
+in
+  mkSource