Allow builders to override failing on pdb mismatch
--- a/build.proj
+++ b/build.proj
@@ -114,6 +114,7 @@
       <SdkSymbolsTarball>$(OutputPath)dotnet-symbols-sdk-$(MicrosoftSourceBuildIntermediateInstallerVersion)-$(TargetRid).tar.gz</SdkSymbolsTarball>
       <SdkLayout>$(ArtifactsTmpDir)Sdk</SdkLayout>
       <SdkTarball>%(SdkTarballItem.Identity)</SdkTarball>
+      <FailOnMissingPDBs Condition="'$(FailOnMissingPDBs)' == ''">true</FailOnMissingPDBs>
     </PropertyGroup>
 
     <MakeDir Directories="$(SdkLayout)" />
@@ -123,7 +124,7 @@
     <CreateSdkSymbolsLayout SdkLayoutPath="$(SdkLayout)"
                             AllSymbolsPath="$(UnifiedSymbolsLayout)"
                             SdkSymbolsLayoutPath="$(SdkSymbolsLayout)"
-                            FailOnMissingPDBs="true" />
+                            FailOnMissingPDBs="$(FailOnMissingPDBs)" />
 
     <Exec Command="tar --numeric-owner -czf $(SdkSymbolsTarball) *"
           WorkingDirectory="$(SdkSymbolsLayout)" />