HostModel: Bundler: Use invariant culture when normalizing file extension (dotnet/core-setup#8551)

The Bundler excludes PDB files by default. When looking for PDB files,
the extension is normalized by using ToLower().
This change fixes the issue to use invariant culture instead.

Commit migrated from https://github.com/dotnet/core-setup/commit/f0fc0c8ef513051e7b7d8d58b375f0d87fa543f9

src/installer/managed/Microsoft.NET.HostModel/Bundle/Bundler.cs

@@ -92,7 +92,7 @@ bool ShouldEmbed(string fileRelativePath)
                 return false;
             }
 
-            if (Path.GetExtension(fileRelativePath).ToLower().Equals(".pdb"))
+            if (Path.GetExtension(fileRelativePath).ToLowerInvariant().Equals(".pdb"))
             {
                 return EmbedPDBs;
             }