WIP: Build wasp in ubuntu:20.04 container

[cprecioso]

Description

Describe your PR! If this PR closes an issue, use “Fixes #(issue_number)" syntax so GitHub will auto-close it when merged.

Select what type of change this PR introduces:

1. Just code/docs improvement (no functional change).
2. Bug fix (non-breaking change which fixes an issue).
3. New feature (non-breaking change which adds functionality).
4. Breaking change (fix or feature that would cause existing functionality to not work as expected).

Update Waspc ChangeLog and version if needed

If you did a bug fix, new feature, or breaking change, that affects waspc, make sure you satisfy the following:

1. I updated ChangeLog.md with description of the change this PR introduces.
2. I bumped waspc version in waspc.cabal to reflect changes I introduced, with regards to the version of the latest wasp release, if the bump was needed.

Add a regression test if needed

If you did a bug fix, make sure you satisfy the following:

1. I added a regression test that reproduces the bug and verifies the fix.

If you're unable to add a regression test, please explain why.
This likely indicates that our current testing setup needs improvement.

Update example apps if needed

If you did code changes and added a new feature, make sure you satisfy the following:

1. I updated waspc/examples/todoApp and its e2e tests as needed and manually checked it works correctly.

If you did code changes and updated an existing feature, make sure you satisfy the following:

1. I updated waspc/examples/todoApp and its e2e tests as needed and manually checked it works correctly.
2. I updated waspc/examples/crud-testing as needed and manually checked it works correctly.
3. I updated waspc/examples/todo-typescript as needed and manually checked it works correctly.
4. I updated waspc/examples/pg-vector-example as needed and manually checked it works correctly.

Update starter apps if needed

If you did code changes and updated an existing feature, make sure you satisfy the following:

1. I updated starter skeleton as needed and manually checked it works correctly.
2. I updated basic starter as needed and manually checked it works correctly.
3. I updated todo-ts starter as needed and manually checked it works correctly.
4. I updated embeddings starter as needed and manually checked it works correctly.
5. I updated saas starter as needed and manually checked it works correctly.

[cprecioso]

Action runs at: https://github.com/wasp-lang/wasp/actions?query=branch:2722-build-our-releases-on-an-older-ubuntu

You can download the example output: https://github.com/wasp-lang/wasp/actions/runs/14996451016

[cprecioso]

Close in favor of #2768