Added patch for writing "delay" to enter u-boot prompt instead of any-key. Also increased bootdelay to 3 seconds to give time to enter the string properly.

Maybe the patch should be selectable via an argument to the build.sh script or something similar.

I've tested these patched builds on my BBB revB with 4GB NAND:

am335x_evm-v2014.10-r3 - works
am335x_evm-v2015.01-rc2-r1 - works
am335x_evm-v2015.01-rc2-72-g85bafb6-r1 - does not work and I have not investigated why, the unit keeps rebooting in a loop, any clue why this build doesn't work?:

####
U-Boot 2015.01-rc2-00089-ga5259bf (Nov 29 2014 - 12:02:51)

       Watchdog enabled
I2C:   ready
DRAM:  512 MiB
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
Using default environment

Net:   <ethaddr> not set. Validating first E-fuse MAC
cpsw, usb_ether
Type <delay> in 3 seconds to get to U-boot-prompt
gpio: pin 53 (gpio 53) value is 1
Card did not respond to voltage select!
Card did not respond to voltage select!
gpio: pin 56 (gpio 56) value is 0
gpio: pin 55 (gpio 55) value is 0
gpio: pin 54 (gpio 54) value is 0
switch to partitions #0, OK
mmc1(part 0) is current device
gpio: pin 54 (gpio 54) value is 1
Checking for: /uEnv.txt ...
Checking for: /boot.scr ...
Checking for: /boot/boot.scr ...
Checking for: /boot/uEnv.txt ...
gpio: pin 55 (gpio 55) value is 1
764 bytes read in 14 ms (52.7 KiB/s)
Loaded environment from /boot/uEnv.txt
Checking if uname_r is set in /boot/uEnv.txt...
gpio: pin 56 (gpio 56) value is 1
Running uname_boot ...
loading /boot/vmlinuz-3.8.13-bone67 ...
5605472 bytes read in 324 ms (16.5 MiB/s)
loading /boot/dtbs/3.8.13-bone67/am335x-boneblack.dtb ...
26098 bytes read in 22 ms (1.1 MiB/s)
loading /boot/initrd.img-3.8.13-bone67 ...
2289346 bytes read in 143 ms (15.3 MiB/s)
debug: [console=ttyO0,115200n8 root=UUID=2b4f2f03-f32c-4bc7-b099-9e4b7de4f4b5 ro rootfstype=ext4 rootwait fixrtc quiet init=/lib/systemd/systemd] ...
debug: [bootz 0x82000000 0x88080000:22eec2 0x88000000] ...
Kernel image @ 0x82000000 [ 0x000000 - 0x558860 ]
## Flattened Device Tree blob at 88000000
   Booting using the fdt blob at 0x88000000
   Loading Ramdisk to 8fdd1000, end 8ffffec2 ... OK
   Loading Device Tree to 8fdc7000, end 8fdd05f1 ... OK
data abort
pc : [<9f758464>]          lr : [<9f78befc>]
sp : 9e72d678  ip : 9e72d680     fp : 9f74f06c
r10: 00000001  r9 : 9e72ded8     r8 : 9e72d6b8
r7 : 9e72d6b0  r6 : 00000001     r5 : 8fdc7000  r4 : 00000214
r3 : 9e72d680  r2 : 00000020     r1 : 9e72d681  r0 : 00000001
Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32
Resetting CPU ...

resetting ...
####