klipper-firmware: build bossac flash binary conditionally (#533029)

pkgs/servers/klipper/klipper-firmware.nix

@@ -20,11 +20,16 @@ args@{
 # are used by flash scripts
 # find those with `rg '\[\"lib'` inside of klipper repo
 let
+  needsBossac =
+    let
+      lines = lib.strings.splitString "\n" (builtins.readFile firmwareConfig);
+    in
+    builtins.any (line: builtins.match "[^#\r\n]*CONFIG_MACH_ATSAMD?=y.*" line != null) lines;
   flashBinaries = [
-    "lib/bossac/bin/bossac"
     "lib/hidflash/hid-flash"
     "lib/rp2040_flash/rp2040_flash"
-  ];
+  ]
+  ++ lib.optional needsBossac "lib/bossac/bin/bossac";
 in
 stdenv.mkDerivation {
   pname = "klipper-firmware-${mcu}";
@@ -41,8 +46,8 @@ stdenv.mkDerivation {
     avrdude
     stm32flash
     pkg-config
-    wxwidgets_3_2 # Required for bossac
-  ];
+  ]
+  ++ lib.optional needsBossac wxwidgets_3_2;
 
   configurePhase = ''
     cp ${firmwareConfig} ./.config