CI: Catch issues similar to #1060

[alexvong243f]

I suggest we should make the source directory read-only in CI, in order to catch issues similar to #1060. What do people think?

The above idea doesn't work. When we run the CI tests, the current directory is actually the home directory, not the source directory. We need to modify the CI in another way.

[cbm755]

Agree this could be useful.

But I like the idea that most of our Makefile is very similar to other packages. In the past we did some effort to make it largely boilerplate. Changes that would benefit other projects seem useful... There might be lower hanging fruit like #1142.