cmake: Toolchain abstraction: Introduce toolchain_cc_warning_base

This is placeholder for base warning flags, common to most toolchains.

The intent here is to abstract Zephyr's dependence on toolchains,
thus allowing for easier porting to other, perhaps commercial,
toolchains and/or usecases.

No functional change expected.

Signed-off-by: Danny Oerndrup <daor@demant.com>
2 files changed