libc/sysdeps: dup3: check for __NR_dup3 since older kernels/arches lack it
libc/sysdeps: dup3: check for __NR_dup3 since older kernels/arches lack it

Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

ndmsystems/uClibc,ndmsystems/uClibc,ndmsystems/uClibc,ndmsystems/uClibc