Renamed this function as it's too generic name for it.
It writes variables, which are used by wic to .env file,
so _write_wic_env is better name for it.
Thanks Christopher Larson for poining out to this.
(From OE-Core rev: f8c7542164ebbe29613532c93ddc34c94238453c)
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>