kbuild: uapi: only use dummy-include for headers which use libc

kbuild: uapi: only use dummy-include for headers which use libc

The headers which do not rely on libc are using built using -nostdinc.
For them the dummy headers are pointless.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-5-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier <nsc@kernel.org>