Add the step to PRs too

Author: premun

eng/pipelines/dotnet-buildtools-prereqs-pr.yml

@@ -30,3 +30,7 @@ stages:
         name: NetCore-Public-XL
         demands: ImageOverride -equals build.ubuntu.2204.amd64.open
         os: linux
+      customBuildInitSteps:
+      - powershell: ./eng/Stage-EngCommon.ps1
+        displayName: Copy eng/common to build dirs
+        condition: eq(variables['Agent.OS'], 'Linux')

eng/pipelines/stages/dotnet-buildtools-prereqs.yml

@@ -26,7 +26,7 @@ stages:
         os: linux
       customBuildInitSteps:
       - powershell: ./eng/Stage-EngCommon.ps1
-        displayName: Stage eng/common in Docker build contexts
+        displayName: Copy eng/common to build dirs
         condition: eq(variables['Agent.OS'], 'Linux')
       - ${{ if eq(variables['System.TeamProject'], 'internal') }}:
         - template: /eng/pipelines/steps/pip-authenticate.yml@self