1. Upgrades both kernels to 6.18.1. 2. Updates the kconfigs to follow the community kconfigcheck and use kconfig fragments. 3. Builds the kernels with LLVM and Clang. Signed-off-by: Aster Boese <asterboese@mailbox.org> Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/7196>