The bcm43xx firmware package contains the source files which we can extract firmware from, broadcom refuses to release their firmware, but the firmware can be extracted from broadcom's binary wireless router module.
Extract the firmware:
b43-fwcutter driver/wl_apsta_mimo.o
Install the firmware:
install -dv ${CLFS}/lib/firmware/b43; cp b43/*.fw ${CLFS}/lib/firmware/b43