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/setup-hooks/validate-pkg-config.sh

@@ -0,0 +1,18 @@
+# This setup hook validates each pkgconfig file in each output.
+
+fixupOutputHooks+=(_validatePkgConfig)
+
+_validatePkgConfig() {
+    local bail=0
+    for pc in $(find "$prefix" -name '*.pc'); do
+        # Do not fail immediately. It's nice to see all errors when
+        # there are multiple pkgconfig files.
+        if ! $PKG_CONFIG --validate "$pc"; then
+            bail=1
+        fi
+    done
+
+    if [ $bail -eq 1 ]; then
+        exit 1
+    fi
+}