allow an override FILE to be honored by test-proxy-tool

Author: scbedd

eng/common/testproxy/test-proxy-tool.yml

@@ -22,11 +22,19 @@ steps:
       pwsh: true
 
   - pwsh: |
-      $version = $(Get-Content "${{ parameters.templateRoot }}/eng/common/testproxy/target_version.txt" -Raw).Trim()
+      $standardVersion = "${{ parameters.templateRoot }}/eng/common/testproxy/target_version.txt"
+      $overrideVersion = "${{ parameters.templateRoot }}/eng/target_proxy_version.txt"
+
+      $version = $(Get-Content $standardVersion -Raw).Trim()
+
+      if (Test-Path $overrideVersion) {
+        $version = $(Get-Content $overrideVersion -Raw).Trim()
+      }
       dotnet tool install azure.sdk.tools.testproxy `
         --tool-path $(Build.BinariesDirectory)/test-proxy `
         --add-source https://pkgs.dev.azure.com/azure-sdk/public/_packaging/azure-sdk-for-net/nuget/v3/index.json `
         --version $version
+      $(Build.BinariesDirectory)/test-proxy --version
     displayName: "Install test-proxy"
     condition: and(succeeded(), ${{ parameters.condition }})