Implement parallel host shader cache compilation.

Ryujinx.Graphics.GAL/IProgram.cs

@@ -4,6 +4,8 @@ namespace Ryujinx.Graphics.GAL
 {
     public interface IProgram : IDisposable
     {
+        ProgramLinkStatus CheckProgramLink(bool blocking);
+
         byte[] GetBinary();
     }
 }

Ryujinx.Graphics.GAL/ProgramLinkStatus.cs

@@ -0,0 +1,9 @@
+namespace Ryujinx.Graphics.GAL
+{
+    public enum ProgramLinkStatus
+    {
+        Incomplete,
+        Success,
+        Failure
+    }
+}