Pin the GitHub Linux machines to 20.04 (#1171)

* Install mono in Linux workflow

* Use ubuntu-20.04 for everything

Author: a-maurice

.github/workflows/build_linux.yml

@@ -38,7 +38,7 @@ on:
 jobs:
   build_desktop:
     name: build-linux-unity${{inputs.unity_version}}-CPP${{ inputs.firebase_cpp_sdk_version }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
 

.github/workflows/build_starter.yml

@@ -60,7 +60,7 @@ env:
 
 jobs:
   check_and_prepare:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     outputs:
       platform: ${{ steps.set_outputs.outputs.platform }}
       release_label: ${{ steps.set_outputs.outputs.release_label }}
@@ -160,7 +160,7 @@ jobs:
 
   decide_build_branch:
     needs: [check_and_prepare,update_versions]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: always()
     outputs: 
       build_branch: ${{ steps.decide_branch.outputs.branch }}

.github/workflows/integration_tests.yml

@@ -40,7 +40,7 @@ env:
 
 jobs:
   check_and_prepare:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     outputs:
       trigger: ${{ steps.set_outputs.outputs.trigger }}
       github_ref: ${{ steps.set_outputs.outputs.github_ref }}
@@ -636,7 +636,7 @@ jobs:
   summarize_results:
     name: "summarize-results"
     needs: [check_and_prepare, build_testapp, playmode_test, integration_test]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: ${{ !cancelled() }}
     steps:
       - uses: actions/checkout@v3

.github/workflows/package.yml

@@ -46,7 +46,7 @@ env:
 jobs:
   package_sdks:
     name: package-${{github.event.inputs.release_label}}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
     steps:
@@ -268,7 +268,7 @@ jobs:
     # Trigger the integration_tests workflow.
     needs: [package_sdks]
     if: (inputs.runIntegrationTests != '0') && !cancelled() && !failure()
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - name: Checkout repo
       uses: actions/checkout@v3

.github/workflows/update_versions.yml

@@ -50,7 +50,7 @@ jobs:
     outputs:
       new_branch: ${{ steps.decide-output.outputs.new_branch }}
       cpp_release_version: ${{ steps.decide_input.outputs.cpp_release_version }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
     steps:

scripts/gha/print_matrix_configuration.py

@@ -57,7 +57,7 @@
 # GitHub Runner
 WINDOWS_RUNNER = "windows-latest"
 MACOS_RUNNER = "macos-13"
-LINUX_RUNNER = "ubuntu-latest"
+LINUX_RUNNER = "ubuntu-20.04"
 
 PARAMETERS = {
   "integration_tests": {