Add PoliCheck exclusion file for upstream sources

.config/PoliCheckExclusions.xml

@@ -0,0 +1,5 @@
+<PoliCheckExclusions>
+  <!-- https://eng.ms/docs/experiences-devices/customer-success-engineering/global/language-as-a-service/validationservices/policheck-for-microsoft/policheckclient/features/features#false-positive-management -->
+  <!-- exclude upstream sources -->
+  <Exclusion Type="FolderPathFull">icu</Exclusion>
+</PoliCheckExclusions>

eng/azure-pipelines.yml

@@ -34,6 +34,7 @@ extends:
         enabled: true
       policheck:
         enabled: true
+        exclusionsFile: $(Build.SourcesDirectory)\.config\PoliCheckExclusions.xml
       binskim:
         scanOutputDirectoryOnly: true
     pool: