FYI;-
Native GCC for up stream OS-Openwrt exists for ages, might be 4~5 years. PACKAGE_gcc and PACKAGE_build-essential is only for x86 platform since hardware limit.
but situation greatly changed since newer router has much powerful hardware.
Linksys WRT1900AC Router (Openwrt based)
CPU: Marvell MV78230-B0 (ARMADA XP) (1.2 GHz, 2 cores)
FLASH: 128 MiB
RAM: 256 MiB
USB 3.0, USB 2.0 / eSATA