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/tools/build-managers/bmake/fix-unexport-env-test.patch

@@ -0,0 +1,13 @@
+--- bmake/unit-tests/unexport-env.mk.orig	2021-05-27 14:44:45.263392298 +0200
++++ bmake/unit-tests/unexport-env.mk	2021-05-27 14:46:46.188881996 +0200
+@@ -4,8 +4,8 @@
+ FILTER_CMD=	grep ^UT_
+ .include "export.mk"
+ 
+-# an example of setting up a minimal environment.
+-PATH=	/bin:/usr/bin:/sbin:/usr/sbin
++# preserve PATH so commands used in the "all" target are still available
++PATH :=	${PATH}
+ 
+ # now clobber the environment to just PATH and UT_TEST
+ UT_TEST=	unexport-env