Fix packaging of PDBs for host binaries

[elinor-fung]

Resolves #38587

After #33716, the PDBs for host binaries are installed to subdirectory instead of right next to the binaries themselves. As a result, they were no longer being put into the symbols packages.

[ghost]

Tagging subscribers to this area: @vitek-karas, @swaroop-sridhar, @agocke
Notify danmosemsft if you want to be subscribed.

[ghost]

Hello @elinor-fung!

Because this pull request has the auto-merge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[vitek-karas]

The failing WASM test log is:

[05:45:27] dbug: test[0]
      [FAIL] System.Numerics.Tests.GetBitLengthTests.RunGetBitLengthTests
      
[05:45:27] dbug: test[0]
      System.OutOfMemoryException : Out of memory
      
[05:45:27] dbug: test[0]
         at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

[vitek-karas]

The CI failure is known and unrelated #38605.