It has been added to glibc in version 2.26.

For some reason, they are in the NDK sources but
they are not available in the tests. I don't know what
Android does here, but nothing that makes sense.

I'd rather avoid the duplication, this is discussed in #707.

They have been added in musl 1.16 but updating musl is non-trivial.

Add missing fexecve() - execute program specified via file descriptor.

Reference: http://pubs.opengroup.org/onlinepubs/9699919799/functions/fexecve.html

Also move them to the common Linux module, as they are not platform-specific.
See include/uapi/linux/falloc.h.

There were previous definitions of SYS_gettid and SYS_perf_event_open

These are all that remain for nix to compile on s390x