Improve CI config file and add nvc++ compiler

[GPMueller]

• refactored and cleaned up
• added nvc++ builds
• updated emscripten
• fixed errors that came up along the way

[codecov[bot]]

Codecov Report

Merging #634 (8e2e810) into update-dependencies (b4ba087) will decrease coverage by 0.32%. The diff coverage is n/a.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## update-dependencies #634 +/- ## ======================================================= - Coverage 48.96% 48.64% -0.32% ======================================================= Files 77 77 Lines 12050 13041 +991 ======================================================= + Hits 5900 6344 +444 - Misses 6150 6697 +547 ```

[coveralls]

Coverage: 80.845%. Remained the same when pulling 8e2e81089675bf7e6def306a0f4ba77270faa5eb on improve-ci-add-nvcpp into be1eac1a7b69c53e338cd02f862fdf29363505f2 on update-dependencies.

[muellan]

@GPMueller what are the qhull-related CMake changes about?

[GPMueller]

After deleting the target branch GH won't let me restore this PR to merge onto develop, so I had to create PR #635