Just a quick check from the administrator's guide:
This file and any auxiliary files used or called by the script will be captured as part of the Base Layer and distributed to the various endpoints. It is important to ensure that the auxiliary files are placed in the same directory as the script or another directory that is captured in the Base Layer.
In order to create a Post-migration script, create a file named post_migration.bat under the %ProgramData%\Wanova\Mirage Service directory. The file must be edited on the reference machine.
Note: The Mirage Client installation includes a default sample script that does not perform any Post-migration script actions.
To monitor the execution of the Post-migration script, Mirage Client reports events to the Mirage central management service if the script returns an error value otherthan zero.