[eng] Set dotnet version before msbuild in security tools pipeline (#26775)

* Update security-tools.yml

* Update security-tools.yml

---------

Co-authored-by: Yunchi Wang <[email protected]>

Author: VeryEarly

.azure-pipelines/security-tools.yml

@@ -31,18 +31,28 @@ jobs:
     condition: eq(variables.IsGenerateBased, true)
     inputs:
       versionSpec: 14.17.1
-
+  
   - task: PowerShell@2
     displayName: Install autorest
     condition: eq(variables.IsGenerateBased, true)
     inputs:
       targetType: inline
       script: npm install autorest@latest;$env:NODE_OPTIONS="--max-old-space-size=65536"
+  - task: UseDotNet@2
+    displayName: 'Use .NET Core sdk 6.0.x for build'
+    inputs:
+      packageType: sdk
+      version: 6.0.x
   - task: PowerShell@2
     displayName: Build
     inputs:
       targetType: inline
       script: dotnet msbuild build.proj /t:"Build;GenerateHelp" /p:"PullRequestNumber=$(System.PullRequest.PullRequestNumber);IsSecurityCheck=true"
+  - task: UseDotNet@2
+    displayName: 'Use .NET Core sdk 8.x for CredScan tools'
+    inputs:
+      packageType: sdk
+      version: 8.x
   - task: securedevelopmentteam.vss-secure-development-tools.build-task-credscan.CredScan@3
     displayName: Run CredScan
     inputs: