Update source-build logic for PR validation

.vsts-ci.yml

@@ -347,10 +347,11 @@ stages:
 
   - template: /src/SourceBuild/Arcade/eng/common/templates/job/source-build-create-tarball.yml
 
-  - ${{ if in(variables['Build.Reason'], 'PullRequest') }}:
-    - template: /src/SourceBuild/Arcade/eng/common/templates/job/source-build-run-tarball-build.yml
-      parameters:
-        dependsOn: Source_Build_Create_Tarball
+  # TODO: Enable once source-build is supported for 8.0 - https://github.com/dotnet/source-build/issues/3026
+  # - ${{ if in(variables['Build.Reason'], 'PullRequest') }}:
+  #   - template: /src/SourceBuild/Arcade/eng/common/templates/job/source-build-run-tarball-build.yml
+  #     parameters:
+  #       dependsOn: Source_Build_Create_Tarball
 
 - ${{ if and(ne(variables['System.TeamProject'], 'public'), notin(variables['Build.Reason'], 'PullRequest')) }}:
   - stage: Publish

src/SourceBuild/Arcade/eng/common/templates/job/source-build-create-tarball.yml

@@ -74,17 +74,3 @@ jobs:
     displayName: Publish BuildLogs
     continueOnError: true
     condition: succeededOrFailed()
-
-  - ${{ if or(eq(variables['System.TeamProject'], 'public'), in(variables['Build.Reason'], 'PullRequest')) }}:
-    # Check if the tarball should be built now so the result can be used in the build tarball job condition.
-    # This prevents allocation of additional agents if the tarball build legs should be skipped.
-    # Only build the tarball if the PR touches source-build source.
-    - script: |
-        if curl "https://api.github.com/repos/dotnet/installer/pulls/$(System.PullRequest.PullRequestNumber)/files" | grep '"filename": "src/SourceBuild/*'
-        then
-          echo "##vso[task.setvariable variable=_includeTarballBuild;isoutput=true]true"
-        fi
-      displayName: Tarball Build Check
-      name: Tarball_Build_Check
-      # Disable tarball CI until .NET 8.0 is source-buildable
-      condition: false

src/SourceBuild/Arcade/eng/common/templates/job/source-build-run-tarball-build.yml

@@ -42,13 +42,13 @@ jobs:
         _EnablePoison: false
         _ExcludeOmniSharpTests: true
         _RunOnline: true
-      CentOSStream8-Offline:
-        _BootstrapPrep: false
-        _Container: ${{ parameters.centOSStream8Container }}
-        _EnablePoison: false
-        _ExcludeOmniSharpTests: true
-        _RunOnline: false
       ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
+        CentOSStream8-Offline:
+          _BootstrapPrep: false
+          _Container: ${{ parameters.centOSStream8Container }}
+          _EnablePoison: false
+          _ExcludeOmniSharpTests: true
+          _RunOnline: false
         CentOSStream9-Offline:
           _BootstrapPrep: false
           _Container: ${{ parameters.centOSStream9Container }}