wic: Extend --rootfs-dir to connect rootfs-dirs

The wic command-line param --rootfs-dir gets generalized to support
multiple directories. Each '--rootfs-dir' could be connected using a
special string, that should be present in .wks. I.e:

wic create ... --rootfs-dir rootfs1=/some/rootfs/dir \
  --rootfs-dir rootfs2=/some/other/rootfs/dir

  part / --source rootfs --rootfs-dir="rootfs1" --ondisk sda --fstype=ext3 \
    --label primary --align 1024

  part /standby --source rootfs --rootfs-dir="rootfs2" \
    --ondisk sda --fstype=ext3 --label secondary --align 1024

The user could use harded-code directory instead of connectors. Like this:

  wic create ... hard-coded-path.wks -r /some/rootfs/dir

  part / --source rootfs --ondisk sda --fstype=ext3 --label primary --align 1024

  part /standby --source rootfs --rootfs-dir=/some/rootfs/dir \
    --ondisk sda --fstype=ext3 --label secondary --align 1024

(From OE-Core rev: 719d093c40e4c259a4c97d6c8a5efb5aeef5fd38)

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/mic/plugins/imager/direct_plugin.py

@@ -42,6 +42,19 @@ from mic.pluginbase import ImagerPlugin
 class DirectPlugin(ImagerPlugin):
     name = 'direct'
 
+    @classmethod
+    def __rootfs_dir_to_dict(self, rootfs_dirs):
+        """
+        Gets a string that contain 'connection=dir' splitted by
+        space and return a dict
+        """
+        krootfs_dir = {}
+        for rootfs_dir in rootfs_dirs.split(' '):
+            k, v = rootfs_dir.split('=')
+            krootfs_dir[k] = v
+
+        return krootfs_dir
+
     @classmethod
     def do_create(self, subcmd, opts, *args):
         """
@@ -63,11 +76,13 @@ class DirectPlugin(ImagerPlugin):
         image_output_dir = args[7]
         oe_builddir = args[8]
 
+        krootfs_dir = self.__rootfs_dir_to_dict(rootfs_dir)
+
         configmgr._ksconf = ksconf
 
         creator = direct.DirectImageCreator(oe_builddir,
                                             image_output_dir,
-                                            rootfs_dir,
+                                            krootfs_dir,
                                             bootimg_dir,
                                             kernel_dir,
                                             native_sysroot,