libuv is in ./libuv and was compiled like so:
$ CC=armeb-linux-gcc AR=armeb-linux-ar make
For anyone googling and finding this (hello, anonymous stranger), check out the following link:
https://forum.openwrt.org/viewtopic.php?id=23246
TL;DR: add "-D_XOPEN_SOURCE=600" to your CFLAGS. See the Makefile below.