Some libc implementation (bionic) is lacking some of the syscall functions
that are present in the glibc.

For those, detect at build time the they are missing and implement a minimal
syscall() wrapper that will essentially give the same result as the glibc
function.
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>