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/fetchdarcs/builder.sh

@@ -0,0 +1,19 @@
+source $stdenv/setup
+
+tagtext=""
+tagflags=""
+if test -n "$rev"; then
+    tagtext="(tag $rev) "
+    tagflags="--tag=$rev"
+elif test -n "$context"; then
+    tagtext="(context) "
+    tagflags="--context=$context"
+fi
+
+header "getting $url $partial ${tagtext} into $out"
+
+darcs get --lazy $tagflags "$url" "$out"
+# remove metadata, because it can change
+rm -rf "$out/_darcs"
+
+stopNest