wic: implement --vars option

This option is used to point wic to the directory with .env
files containing list of bitbake variables and their values.

If this option is used wic will get bitbake variables from
files instead of parsing 'bitbake -e' output.

The main reason for this is to support new mode, when bitbake
runs wic to produce wic images. In this case wic can't run bitbake
again as it's locked, so it will get variables from .env files.

(From OE-Core rev: abdfad1cd68fcd7387c2a508ab81512e8f6b93ce)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/wic

@@ -114,6 +114,9 @@ def wic_create_subcommand(args, usage_str):
     parser.add_option("-c", "--compress-with", choices=("gzip", "bzip2", "xz"),
                       dest='compressor',
                       help="compress image with specified compressor")
+    parser.add_option("-v", "--vars", dest='vars_dir',
+                      help="directory with <image>.env files that store "
+                           "bitbake variables")
     parser.add_option("-D", "--debug", dest="debug", action="store_true",
                       default=False, help="output debug information")
 
@@ -146,6 +149,9 @@ def wic_create_subcommand(args, usage_str):
     else:
         options.build_check = False
 
+    if options.vars_dir:
+        BB_VARS.vars_dir = options.vars_dir
+
     if options.build_check:
         print "Checking basic build environment..."
         if not engine.verify_build_env():