Fix the download path issues

Variables in rules are seemingly replaced at use-time,
not at parse-time. That has been causing issues if
vendor/cm/terminal/Android.mk wasn't the last Makefile
to set LOCAL_PATH, which is the case if devices use
Android.mk files that are included during the device
configuration phase.

Copy the current LOCAL_PATH into an variable that
doesn't get overwritten and replace current usages of
LOCAL_PATH inside rules by the new variable.

Change-Id: I8ff93ad45ef30f8d338c1622f183293ca9f38fdf