arm-autonomy/wic: Introduce empty plugin to create unformatted empty partitions

The empty wic plugin is used to create unformatted empty partitions for wic
images.

To use it you must pass "empty" as argument for the "--source" parameter in the
wks file. For example:
part foo --source empty --ondisk sda --size="1024" --align 1024

Change-Id: I0155561e9cc2ac11159e181eec9e4d9ae11555c3
Issue-Id: SCM-889
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-autonomy/scripts/lib/wic/plugins/source/empty.py

@@ -0,0 +1,32 @@
+#
+# SPDX-License-Identifier: MIT
+#
+
+# The empty wic plugin is used to create unformatted empty partitions for wic
+# images.
+# To use it you must pass "empty" as argument for the "--source" parameter in
+# the wks file. For example:
+# part foo --source empty --ondisk sda --size="1024" --align 1024
+
+import logging
+
+from wic.pluginbase import SourcePlugin
+
+logger = logging.getLogger('wic')
+
+class EmptyPartitionPlugin(SourcePlugin):
+    """
+    Populate unformatted empty partition.
+    """
+
+    name = 'empty'
+
+    @classmethod
+    def do_prepare_partition(cls, part, source_params, cr, cr_workdir,
+                             oe_builddir, bootimg_dir, kernel_dir,
+                             rootfs_dir, native_sysroot):
+        """
+        Called to do the actual content population for a partition i.e. it
+        'prepares' the partition to be incorporated into the image.
+        """
+        return