I am compiling the module in multilib

defaulttune is aarch64 and the usermode 32 bit.

how can i give toolchain path in .bb file.Is it with 

EXTRA_OEMAKE += "${TARGET_SYS}"

or

EXTRA_OEMAKE   += "${TARGET_PREFIX}"

I am getting arm-rdkmllib32-linux-gnueabi-gcc not found error.

Best Regards,