[CI] Change how we define the matrix

# Motivation

# Modification

# Result

.github/workflows/pull_request.yml

@@ -16,7 +16,7 @@ jobs:
   unit-tests:
     name: Unit tests
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
+    uses: ./.github/workflows/unit_tests.yml@main
     with:
       linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
       linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"

.github/workflows/swift_matrix.yml

@@ -148,17 +148,21 @@ jobs:
           apt-get -qq update && apt-get -qq -y install curl
           curl -s https://raw.githubusercontent.com/apple/swift-nio/main/scripts/check-matrix-job.sh | bash
 
+  generate-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+    - id: set-matrix
+      run: echo "::set-output name=matrix::{\"swift\":[{\"image\":\"swift:6.0-windowsservercore-ltsc2022\",\"swift_version\":\"6.0\",\"enabled\":true}]}"
+
   windows:
     name: Windows (${{ matrix.swift.swift_version }})
+    needs: generate-matrix
     runs-on: windows-2022
     strategy:
       fail-fast: false
-      matrix:
-        # We are specifying only the major and minor of the docker images to automatically pick up the latest patch release
-        swift:
-          - image: swift:6.0-windowsservercore-ltsc2022
-            swift_version: "6.0"
-            enabled: ${{ inputs.matrix_windows_6_0_enabled }}
+      matrix: ${{fromJson(needs.generate-matrix.outputs.matrix)}}
     steps:
       - name: Pull Docker image
         if: ${{ matrix.swift.enabled }}

.github/workflows/unit_tests.yml

@@ -73,7 +73,7 @@ jobs:
   unit-tests:
     name: Unit tests
     # Workaround https://github.com/nektos/act/issues/1875
-    uses: apple/swift-nio/.github/workflows/swift_matrix.yml@main
+    uses: ./.github/workflows/swift_matrix.yml@main
     with:
       name: "Unit tests"
       matrix_linux_command: "swift test"