Building for core18: multipass issue

I’m getting this issue when trying to build a package:

$ multipass launch
One quick question before we launch … Would you like to help                    
the Multipass developers, by sending anonymous usage data?
This includes your operating system, which images you use,
the number of instances, their properties and how long you use them.
We’d also like to measure Multipass’s speed.

Send usage data (yes/no/Later)? no

Launched: spruce-dugong                                   
# multipass itself is working fine                      
$ snapcraft 
Launching a VM.
launch failed: Downloaded image hash does not match                             
An error occurred when trying to launch the instance with 'multipass': returned exit code 2.
Ensure that 'multipass' is setup correctly and try again.

The most annoying thing is that it redownloads the image each time so that debugging this is really painful. Are there workarounds for this issue?

I can’t even use cleanbuild instead :’(

snapcraft cleanbuild
The cleanbuild command is no longer supported when using the base keyword.

How do I directly build on the host system, nowadays?

Thanks a lot for your help!