package/libuv: fix support for uClibc-ng

See https://bugs.busybox.net/show_bug.cgi?id=8296 for further details on
the origins of this bug.

Submitted upstream to libuv and accepted, see
https://github.com/libuv/libuv/pull/653 and
https://github.com/libuv/libuv/commit/c861972



Signed-off-by: Martin Bark <martin@barkynet.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>