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/tools/backup/btar/default.nix

@@ -0,0 +1,36 @@
+{ lib, stdenv, fetchurl, fetchpatch, librsync }:
+
+stdenv.mkDerivation rec {
+  pname = "btar";
+  version = "1.1.1";
+
+  src = fetchurl {
+    url = "https://vicerveza.homeunix.net/~viric/soft/btar/btar-${version}.tar.gz";
+    sha256 = "0miklk4bqblpyzh1bni4x6lqn88fa8fjn15x1k1n8bxkx60nlymd";
+  };
+
+  patches = [
+    (fetchpatch {
+      url = "https://build.opensuse.org/public/source/openSUSE:Factory/btar/btar-librsync.patch?rev=2";
+      sha256 = "1awqny9489vsfffav19s73xxg26m7zrhvsgf1wxb8c2izazwr785";
+    })
+  ];
+
+  # Workaround build failure on -fno-common toolchains like upstream
+  # gcc-10. Otherwise build fails as:
+  #   ld: listindex.o:/build/btar-1.1.1/loadindex.h:12: multiple definition of
+  #     `ptr'; main.o:/build/btar-1.1.1/loadindex.h:12: first defined here
+  NIX_CFLAGS_COMPILE = "-fcommon";
+
+  buildInputs = [ librsync ];
+
+  makeFlags = [ "PREFIX=$(out)" ];
+
+  meta = with lib; {
+    description = "Tar-compatible block-based archiver";
+    license = lib.licenses.gpl3Plus;
+    homepage = "https://viric.name/cgi-bin/btar";
+    platforms = platforms.all;
+    maintainers = with maintainers; [ viric ];
+  };
+}