Better build output from `ionic build`, number of errors is not clear

I’m working on an Ionic/Angular app migration from v3 to v5 and after creating a sample app and moving files around and adding updated dependencies got lots of build errors from ionic build command:

[ERROR] An error occurred while running subprocess ng.
ng run app:build exited with exit code 1.

While the errors are expected and I’m working my way through them, the number of errors left is not clear. The build output is not complete (when I scroll up I cannot reach the first error) and also ionic build (or rather ng run) doesn’t give me the exact number of errors so I can understand the progress.

How can I track number or errors from the build output?