blinky app won't build unless upgrading to newer arm-toolchain

[manish-sudo]

Following instructions here if I install the 4.9 arm toolchain, and build the app, I get following error message:

$ newt create-image nrf52_blinky 1.0.0 Compiling repos/apache-mynewt-core/hw/drivers/uart/src/uart.c Assembling repos/apache-mynewt-core/hw/bsp/nordic_pca10040/src/arch/cortex_m4/gcc_startup_nrf52.s Assembling repos/apache-mynewt-core/hw/bsp/nordic_pca10040/src/arch/cortex_m4/gcc_startup_nrf52_split.s Compiling repos/apache-mynewt-core/hw/bsp/nordic_pca10040/src/sbrk.c Compiling repos/apache-mynewt-core/hw/hal/src/hal_common.c . . . . . . Compiling repos/apache-mynewt-core/libc/baselibc/src/memfile.c Compiling repos/apache-mynewt-core/libc/baselibc/src/memmem.c Error: repos/apache-mynewt-core/kernel/os/src/os_mempool.c: In function 'os_memblock_from': repos/apache-mynewt-core/kernel/os/src/os_mempool.c:308:5: error: implicit declaration of function 'static_assert' [-Werror=implicit-function-declaration] static_assert(sizeof block_addr == sizeof baddr32, ^ cc1: all warnings being treated as errors

After advancing the toolchain to "version 8.2.1 20181213", the above mentioned problem was resolved. So, I think the document should be updated to avoid this issue.