Work around unsupported base image

dotnet/sdk#31893

Author: jaredpar

azure-pipelines-compiler.yml

@@ -191,7 +191,8 @@ stages:
         - job: Linux
           pool:
             ${{ if or(ne(variables['System.TeamProject'], 'internal'), in(variables['Build.Reason'], 'Manual', 'PullRequest', 'Schedule')) }}:
-              vmImage: ubuntu-latest
+              name: NetCore-Public
+              demands: ImageOverride -equals Build.Ubuntu.1804.Amd64
             ${{ if and(eq(variables['System.TeamProject'], 'internal'), notin(variables['Build.Reason'], 'Manual', 'PullRequest', 'Schedule')) }}:
               name: NetCore1ESPool-Internal
               demands: ImageOverride -equals Build.Ubuntu.1804.Amd64

azure-pipelines.yml

@@ -362,7 +362,8 @@ stages:
           options: --init # This ensures all the stray defunct processes are reaped.
         pool:
           ${{ if eq(variables['System.TeamProject'], 'public') }}:
-            vmImage: ubuntu-latest
+            name: NetCore-Public
+            demands: ImageOverride -equals Build.Ubuntu.1804.Amd64
           ${{ if eq(variables['System.TeamProject'], 'internal') }}:
             name: $(DncEngInternalBuildPool)
             demands: ImageOverride -equals Build.Ubuntu.1804.Amd64