Fix builds on macOS / Linux using the build.sh script

[filipnavara]

Fix builds on macOS / Linux using the build.sh script

• You've read the Contributor Guide and Code of Conduct.
• You've included unit or integration tests for your change, where applicable.
• You've included inline docs for your change, where applicable.
• If any gains or losses in performance are possible, you've included benchmarks for your changes. More info
• There's an open issue for the PR that you are making. If you'd like to propose a new feature or change, please open an issue to discuss the change or find an existing issue.

Description

The builds are broken on macOS / Linux due to references to non-existing files and tests being compiled against wrong assets (eg. net6+ tests with Span APIs trying to use netstandard2.0 assets).

[jmprieur]

LGTM
Thanks @filipnavara

[jennyf19]

Thanks so much @filipnavara