Yes, you can use the offical Nordic SDK and a J-Link programmer. The Arch BLE’s SWCLK and SWDIO are available for external programmer. Actually the on-board CMSIS DAP interface of the Arch BLE is quite powerful. We don’t have to a J-Link programmer. With the latest firmware of CMSIS DAP interface (following the wiki to update firmware), we can drag-n-drop a softdevice hex file and then drag-n-drop an application hex file, or drag-n-drop a merged hex file.
If you just want a offline toolchain, try https://github.com/Seeed-Studio/mbed_ble. There is also a bootloader for the Arch BLE. We can drag-n-drop the bootloader hex file after flashing a softdevice and an application.