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>

nixos/doc/manual/development/running-nixos-tests.section.md

@@ -0,0 +1,31 @@
+# Running Tests {#sec-running-nixos-tests}
+
+You can run tests using `nix-build`. For example, to run the test
+[`login.nix`](https://github.com/NixOS/nixpkgs/blob/master/nixos/tests/login.nix),
+you just do:
+
+```ShellSession
+$ nix-build '<nixpkgs/nixos/tests/login.nix>'
+```
+
+or, if you don't want to rely on `NIX_PATH`:
+
+```ShellSession
+$ cd /my/nixpkgs/nixos/tests
+$ nix-build login.nix
+…
+running the VM test script
+machine: QEMU running (pid 8841)
+…
+6 out of 6 tests succeeded
+```
+
+After building/downloading all required dependencies, this will perform
+a build that starts a QEMU/KVM virtual machine containing a NixOS
+system. The virtual machine mounts the Nix store of the host; this makes
+VM creation very fast, as no disk image needs to be created. Afterwards,
+you can view a log of the test:
+
+```ShellSession
+$ nix-store --read-log result
+```