avoid SELinux compile error and keep radio flag effective

Bug: 209886647
Test: build pass with dmd and vcd not in the ROM
Change-Id: I5a52e74a2c7ef600e8314844c261b3a25ad4a737
diff --git a/modem/userdebug.mk b/modem/userdebug.mk
index 87697a7..4fcab64 100644
--- a/modem/userdebug.mk
+++ b/modem/userdebug.mk
@@ -1,2 +1,4 @@
-PRODUCT_PACKAGES += vcd
+ifneq ($(BOARD_WITHOUT_RADIO),true)
+  PRODUCT_PACKAGES += vcd
+endif
 BOARD_VENDOR_SEPOLICY_DIRS += device/google/gs101-sepolicy/modem/userdebug/