What toolchain you are using? I personally compiled agent for OpenWRT running on Atheros AR7240 (MIPS 24Kc) using standard buildroot-based environment.
Btw, if you are compiling for OpenWRT – you can use our feed: https://github.com/netxms/openwrt-feed
Btw, if you are compiling for OpenWRT – you can use our feed: https://github.com/netxms/openwrt-feed