Add _kernel_on_diet customization option (#805)

* prepare: remove prompt for modprobed.db

it's an advanced feature, we don't want to prompt it
just like with TCP congestion algos

* add "_kernel_on_diet" customization option

A little less sugar intake is always welcome
this option hopefully helps with building kernels in github ci

* prepare: fix typo in var name $_where

the underscore was forgotten all this time...

* ci: enable _kernel_on_diet

* ci: move away from deprecated feature

the new approach is better actually too
https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

customization.cfg

@@ -51,6 +51,12 @@ _force_all_threads="true"
 # Set to true to prevent ccache from being used and set CONFIG_GCC_PLUGINS=y (which needs to be disabled for ccache to work properly)
 _noccache="false"
 
+# [Experimental] Build only a subset of the default kernel modules list to speedup compile time and lower needed space to build kernel
+#                Notes:
+#                - If the kernel fails to boot with this option active, disable it and rebuild
+#                - This option cannot be used with _modprobeddb="true"
+_kernel_on_diet="false"
+
 # Set to true to use modprobed db to clean config from unneeded modules. Speeds up compilation considerably. Requires root - https://wiki.archlinux.org/index.php/Modprobed-db
 # Using this option can trigger user prompts if the config doesn't go smoothly.
 # !!!! Make sure to have a well populated db !!!! - Leave empty to be asked about it at build time