[U-Boot] Building u-boot for iMX28 and getting error in mkimage of missing command line parameter CONFIG_IMX_CONFIG

[Bill]

All,

     I am working on building the latest u-boot for the imx28evk board.  
I have done the following steps:

1. git clone git://git.denx.de/u-boot-imx.git
2. setup paths for finding my cross-compiler
1.  make mx28evk_config
2.  make u-boot.imx
3.  It then gets through most of the build process and then fails on 
this command line:

                $ tools/mkimage -n -T imximage -e 0x40000100 -d 
u-boot.bin u-boot.imx

after more digging, its looks like the CONFIG_IMX_CONFIG var is not 
getting filled in (I believe this value should follow the -n parameter)

Thanks,
Bill