Ship SoundIO library only for the specified runtime (#3103)

* Add RuntimeIdentifers properties

For Linux, Windows and OS X x86-64
This ensures that the SoundIO project gets this property when built as a subproject

* Address gdkchan's nit

Merge tags into one

Ryujinx.Audio.Backends.SoundIo/Ryujinx.Audio.Backends.SoundIo.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <RuntimeIdentifiers>win-x64;linux-x64;osx-x64</RuntimeIdentifiers>
   </PropertyGroup>
 
   <ItemGroup>