How is a directory referred to in the bootstrapper?

[sszeller]

The installer for SQL Server Express 2019 has a command line option UPDATESOURCE which is intended to provide the location of any updates that should be applied.

I am bundling the SS2019 installer and the latest SS Cumulative Update as a prerequisite to an application I'm installing. The directory structure that I'm using is as follows:

 Bundle.wxs
 Prerequisites (directory)
      SqlServerExpress2019 (directory)
           SQLEXPR_x64_ENU.exe
      SqlServerUpdates (directory)
           SQLServer2019-KB5004524-x64.exe

When SQLEXPR_x64 is called, it is passed a directory name that it should extract its contents to (C:\Temp\SS2019, for example).

UPDATESOURCE should point to the location of the update (SQLServer2019-KB5004524-x64.exe).

... and this is where I'm stuck.

Do I put SQLServer2019-KB5004524-x64.exe as a Payload item? If so, how do I refer to it (with regard to the value of UPDATESOURCE)?

Or would it be better to have it as its own separate package (rather than trying to chain it to the SS2019 installer)? This would obviate the need for UPDATESOURCE.

Or is there another way recommended?