init: deduplicate cc-can-link.sh invocations

init: deduplicate cc-can-link.sh invocations

The command to invoke scripts/cc-can-link.sh is very long and new usages
are about to be added.

Add a helper variable to make the code easier to read and maintain.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20251114-kbuild-userprogs-bits-v3-2-4dee0d74d439@linutronix.de
Signed-off-by: Nicolas Schier <nsc@kernel.org>