b43Firmware: support cross compile

pkgs/os-specific/linux/firmware/b43-firmware-cutter/default.nix

@@ -11,7 +11,10 @@ stdenv.mkDerivation rec {
 
   patches = [ ./no-root-install.patch ];
 
-  makeFlags = [ "PREFIX=$(out)" ];
+  makeFlags = [
+    "PREFIX=$(out)"
+    "CC=${stdenv.cc.targetPrefix}cc"
+  ];
 
   meta = {
     description = "Firmware extractor for cards supported by the b43 kernel module";

pkgs/os-specific/linux/firmware/b43-firmware/5.1.138.nix

@@ -11,7 +11,7 @@ stdenv.mkDerivation {
     sha256 = "0vz4ka8gycf72gmnaq61k8rh8y17j1wm2k3fidxvcqjvmix0drzi";
   };
 
-  buildInputs = [ b43FirmwareCutter ];
+  nativeBuildInputs = [ b43FirmwareCutter ];
 
   installPhase = ''
     mkdir -p $out/lib/firmware

pkgs/os-specific/linux/firmware/b43-firmware/6.30.163.46.nix

@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
     sha256 = "0baw6gcnrhxbb447msv34xg6rmlcj0gm3ahxwvdwfcvq4xmknz50";
   };
 
-  buildInputs = [ b43FirmwareCutter ];
+  nativeBuildInputs = [ b43FirmwareCutter ];
 
   sourceRoot = ".";