Had the same line 73 issue :
E: Can't symlink /system/xbin/bb/dirname
E: FAilure at line 73:
symlink /system/xbin/busybox SYSTEMbin/bb/dirname
I think this a loss of root problem like another install issue on here. I try to turn on USB-MS and it tells me to do so from the console.
I came from CM220.127.116.11 and wiped (fact reset, dalvik, ext) multiple times.