Add warning and update PR checks for Swift on Linux (#2399)

* PR checks: Only run Swift build command on MacOS
* PR checks: update to only test Swift on MacOS
* Log warning if workflow is running Swift on Ubuntu
---------

Co-authored-by: Andrew Eisenberg <aeisenberg@github.com>

.github/workflows/__unset-environment.yml

@@ -27,6 +27,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - os: ubuntu-latest
+            version: stable-20230403
+          - os: ubuntu-latest
+            version: stable-v2.13.5
+          - os: ubuntu-latest
+            version: stable-v2.14.6
+          - os: ubuntu-latest
+            version: stable-v2.15.5
+          - os: ubuntu-latest
+            version: stable-v2.16.6
           - os: ubuntu-latest
             version: default
           - os: ubuntu-latest
@@ -65,10 +75,9 @@ jobs:
         id: init
         with:
           db-location: ${{ runner.temp }}/customDbLocation
+      # Swift is not supported on Ubuntu so we manually exclude it from the list here
+          languages: cpp,csharp,go,java,javascript,python,ruby
           tools: ${{ steps.prepare-test.outputs.tools-url }}
-      - uses: ./../action/.github/actions/setup-swift
-        with:
-          codeql-path: ${{ steps.init.outputs.codeql-path }}
       - uses: actions/setup-go@v5
         with:
           go-version: '>=1.21.0'