@vchong: Thanks for the links!
I flashed the 16.06 RPB images (except I used jessie developer for my rootfs instead of jessie alip) via fastboot. Then I removed the link 5-6 from the J601 header and powered up the board.
I see the grub prompt from the console side:
GNU GRUB version 2.02~beta2-33.linarojessie.6
Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists possible
device or file completions.
Is this normal behaviour? I wanted to check before I go through the build instructions.