Prevent restore from deleting mibc cache file (#91220)

Restore should not remove the mibc cache file that is
used to enable incrementalism when merging mibc files.

This fixes an issue with the logic introduced in
454057de49, which
was tested on incremental builds without restore.

eng/restore/optimizationData.targets

@@ -1,4 +1,4 @@
-<Project>
+<Project>
   <ItemGroup>
     <!-- Mibc data to use when exact architecture match is available -->
     <MIBCPackageDef Include="optimization.windows_nt-x86.mibc.runtime" Version="$(optimizationwindows_ntx86MIBCRuntimeVersion)" MibcArchitecture="windows/x86"/>
@@ -25,6 +25,9 @@
   <Target Name="GetMIBCData"
           AfterTargets="Restore">
 
+    <PropertyGroup>
+      <_MergeMibcFilesCacheFile>$(MibcOptimizationDataDir)/$(TargetOS)/$(TargetArchitecture)/merge_mibc_files.cache</_MergeMibcFilesCacheFile>
+    </PropertyGroup>
     <ItemGroup>
       <MIBCPackage>
         <PackagePath>$(NuGetPackageRoot)%(MIBCPackage.Identity)/%(MIBCPackage.Version)</PackagePath>
@@ -32,7 +35,7 @@
       <_optimizationMibcFile Include="%(MIBCPackage.PackagePath)/**/*.mibc" SubdirectoryName="$(TargetOS)/$(TargetArchitecture)" />
       <_optimizationMibcDestinationFile Include="@(_optimizationMibcFile->'$(MibcOptimizationDataDir)%(SubdirectoryName)/%(RecursiveDir)%(Filename)%(Extension)')" />
       <ExcessFilesCurrentlyPresent Include="$(MibcOptimizationDataDir)/**" 
-                                   Exclude="@(_optimizationMibcDestinationFile)"/>
+                                   Exclude="@(_optimizationMibcDestinationFile);$(_MergeMibcFilesCacheFile)"/>
     </ItemGroup>
 
     <Error Condition="'@(_optimizationMibcFile)' == ''" Text="Failed to restore Mibc optimization data" />