CustomActionExecute

Used in WiXCustomAction for determing when to run the custom action

Union Case	Description
`Commit` Signature:	Indicates that the custom action will run after successful completion of the installation script (at the end of the installation).
`Deferred` Signature:	Indicates that the custom action runs in-script (possibly with elevated privileges).
`FirstSequence` Signature:	Indicates that the custom action will only run in the first sequence that runs it.
`Immediate` Signature:	Indicates that the custom action will run during normal processing time with user privileges. This is the default.
`OncePerProcess` Signature:	Indicates that the custom action will only run in the first sequence that runs it in the same process.
`Rollback` Signature:	Indicates that a custom action will run in the rollback sequence when a failure occurs during installation, usually to undo changes made by a deferred custom action.
`SecondSequence` Signature:	Indicates that a custom action should be run a second time if it was previously run in an earlier sequence.