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/development/perl-modules/expression-generator/lib-cache.sh

@@ -0,0 +1,18 @@
+
+# First argument: command to run
+# Second argument: cache name
+# Third argument: argument to command
+# Fourth argument: cache type
+cached_output () {
+    cmd="$1";
+    basename="$2";
+    arg="$3";
+    ext="$4";
+
+    if ! [ -e "cache-${ext//./-}/${basename}.${ext}" ]; then
+        mkdir -p "cache-${ext//./-}";
+        $cmd $arg > "cache-${ext//./-}/${basename}.${ext}";
+    fi;
+
+    cat "cache-${ext//./-}/${basename}.${ext}";
+}