build: target_config_lib: do not build unused packages for targets without opkg

Normally, we build all nonshared packages (which includes all kernel
modules) to generate an opkg feed for later package installations by
users. On targets without opkg, this just wastes time - disable it.

scripts/target_config_lib.lua

@@ -139,6 +139,7 @@ lib.check_devices()
 if not lib.opkg then
 	lib.config('SIGNED_PACKAGES', false)
 	lib.config('CLEAN_IPKG', true)
+	lib.config('ALL_NONSHARED', false)
 	lib.packages {'-opkg'}
 end
 

targets/generic

@@ -40,7 +40,7 @@ config('PACKAGE_kmod-jool', false) -- fails to build
 config('BUSYBOX_CUSTOM', true)
 config('BUSYBOX_CONFIG_FEATURE_PREFER_IPV4_ADDRESS', false)
 
-config('PACKAGE_ATH_DEBUG', true)
+try_config('PACKAGE_ATH_DEBUG', true)
 
 try_config('TARGET_SQUASHFS_BLOCK_SIZE', 256)