Flow:
Modifying a kernel flag of string type (flag example below) in the filename: sonic-linux-kernel/patch/kconfig-inclusions.
the expectation is that after the kernel build we should found a kernel .config file including this modification, but its not happened.
The kernel flag in the /linux-5.10.46/debian/build/build_amd64_none_amd64/.config remained like was at before the modification in the kconfig-inclusions.

kernel flag example:
CONFIG_SYSTEM_TRUSTED_KEYS="debian/certs/new_cert.key

How to repro:
tested on branch: master

1. add a line in kconfig-inclusions file with the kernel flag, i.e

CONFIG_SYSTEM_TRUSTED_KEYS="debian/certs/new_cert.key

2. make the kernel
3. read the kernel .config file created in /linux-5.10.46/debian/build/build_amd64_none_amd64/.config
4. check the value of the keyname CONFIG_SYSTEM_TRUSTED_KEYS.

Note:
I think the problem is happening just with kernel flags that contain some string default values, like in this case:
CONFIG_SYSTEM_TRUSTED_KEYS have a default value of "debian/certs/debian-uefi-certs.pem