modeld: avoid using USB GPU on a AMD laptop (#35602)

modeld: avoid using usb GPU if 'USBGPU' is not in os.environ

Co-authored-by: Adeeb Shihadeh <adeebshihadeh@gmail.com>

selfdrive/modeld/SConscript

@@ -56,17 +56,15 @@ for model_name in ['driving_vision', 'driving_policy', 'dmonitoring_model']:
   tg_compile(flags, model_name)
 
 # Compile BIG model if USB GPU is available
-import subprocess
-from tinygrad import Device
-
-# because tg doesn't support multi-process
-devs = subprocess.check_output('python3 -c "from tinygrad import Device; print(list(Device.get_available_devices()))"', shell=True, cwd=env.Dir('#').abspath)
-if b"AMD" in devs:
-  del Device
+if "USBGPU" in os.environ:
+  import subprocess
+  # because tg doesn't support multi-process
+  devs = subprocess.check_output('python3 -c "from tinygrad import Device; print(list(Device.get_available_devices()))"', shell=True, cwd=env.Dir('#').abspath)
+  if b"AMD" in devs:
     print("USB GPU detected... building")
     flags = "AMD=1 AMD_IFACE=USB AMD_LLVM=1 NOLOCALS=0 IMAGE=0"
     bp = tg_compile(flags, "big_driving_policy")
     bv = tg_compile(flags, "big_driving_vision")
     lenv.SideEffect('lock', [bp, bv])  # tg doesn't support multi-process so build serially
-else:
+  else:
     print("USB GPU not detected... skipping")