config: fix recursive deps

The latest kconfig stuff is more stringent when it comes to validating
the dependency of the symbols. It is no longer possible to have a symbol
depend on itself (such as our construct for arch/cc/libc/... was doing).

Fix our generated-file infrastructure to avoid these situations when the
new kconfig stuff will be merged (in a following changeset).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

 reporter_comment="Example for building a toolchain for m68000 bare metal targets"