Fix interface handling in CorInfoImpl.resolveVirtualMethod (#3922)

Without this fix, the CoreRT compiler generated the following code for the
test that I am adding:

call    Interfaces!_NewHelper_Interfaces_BringUpTest_SomeClass
mov     rcx,rax
call
Interfaces!Interfaces_BringUpTest_SomeAbstractBaseClass__get_SomeValue

As you can see, it ends up calling an abstract method on the base class.

With this fix, the interface call is resolved correctly:

call    Interfaces!_NewHelper_Interfaces_BringUpTest_SomeClass
mov     rcx,rax
call    Interfaces!Interfaces_BringUpTest_SomeClass__get_SomeValue

src/JitInterface/src/CorInfoImpl.cs

@@ -849,6 +849,10 @@ namespace Internal.JitInterface
                 }
 
                 impl = implType.ResolveInterfaceMethodTarget(decl);
+                if (impl != null)
+                {
+                    impl = implType.GetClosestDefType().FindVirtualFunctionTargetMethodOnObjectType(impl);
+                }
             }
             else
             {

tests/src/Simple/Interfaces/Interfaces.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Text;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 
 public class BringUpTest
 {
@@ -28,6 +29,9 @@ public class BringUpTest
         if (TestSpecialArrayInterfaces() == Fail)
             return Fail;
 
+        if (TestIterfaceCallOptimization() == Fail)
+            return Fail;
+
         return Pass;
     }
 
@@ -359,4 +363,34 @@ public class BringUpTest
     }
 
     #endregion
+
+    #region Interface call optimization tests
+
+    public interface ISomeInterface
+    {
+        int SomeValue { get; }
+    }
+
+    public abstract class SomeAbstractBaseClass : ISomeInterface
+    {
+        public abstract int SomeValue { get; }
+    }
+
+    public class SomeClass : SomeAbstractBaseClass
+    {
+        public override int SomeValue
+        {
+            [MethodImpl(MethodImplOptions.NoInlining)]
+            get { return 14; }
+        }
+    }
+
+    private static int TestIterfaceCallOptimization()
+    {
+        ISomeInterface test = new SomeClass();
+        int v = test.SomeValue;
+        return (v == 14) ? Pass : Fail;
+    }
+
+    #endregion
 }