export PATH=~/Your_Toolchain_PATH/ 
for_example  /alps/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin:$PATH

Buile command:

uboot
=====
cd <uboot path>
TARGET_PRODUCT=jrdhz75_gb2 make jrdhz75_gb2_config
TARGET_PRODUCT=jrdhz75_gb2 make 

kernel
======
cd <kernel path>
cp mediatek-configs .config
TARGET_PRODUCT=jrdhz75_gb2 MTK_ROOT_CUSTOM=../mediatek/custom make