run fast tests on linux-CI as well (#960)

That way we can see if these archives work like they should if there
is a case-sensitivity mismatch.

If not, there should be a way to fix this, and CI should protect from
regression.

Author: Byron

.github/workflows/ci.yml

@@ -60,6 +60,7 @@ jobs:
         os:
           - windows-latest
           - macos-latest
+          - ubuntu-latest
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3