musl/linux-headers: add <linux/libc-compat.h> a compatibility interface for userspace libc header coordination

Origin: https://github.com/sabotage-linux/kernel-headers/blob/master/generic/include/linux/libc-compat.h
musl/linux-header: use libc-compat.h to avoid redefinition errors for 'struct ethhdr'
cpio: changed build priority (102.050 -> 108.400) to be build after tar

Detected when cross-compiling
ebtables: fixed installation when cross-compiling when DESTDIR is effective
ebtables: changed to use system kernel headers instead of the included ones