Add test which compiles the example plugin against release package.

[karliss]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've updated the documentation with the relevant information (if needed)

Detailed description

Goals:

• test that sample cpp plugin can be compiled
• test that it is possible to compile a plugin against release package binaries and all the required files are included (within reason)

Test plan (required)

• CI builds are green
• inspect the CI logs

Also recently manually tested that plugins compiled in similar manner can be loaded into the cutter.

Closing issues

Closes #3372