Add interpreter test

The test contains one application that contains a method named `RunInterpreterTests` serving as the interpreter entry point. This application is built only, as it is not the test itself. This application is executed with corerun by the actual test, which waits for the corerun exit code to determine success.

Author: BrzVlad

src/coreclr/interpreter/compiler.cpp

@@ -515,6 +515,9 @@ int InterpCompiler::GenerateCode(CORINFO_METHOD_INFO* methodInfo)
         uint8_t opcode = *ip;
         switch (opcode)
         {
+            case CEE_NOP:
+                ip++;
+                break;
             case CEE_LDC_I4_M1:
             case CEE_LDC_I4_0:
             case CEE_LDC_I4_1:

src/tests/JIT/interpreter/Interpreter.cs

@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+
+public class InterpreterTest
+{
+    static int Main(string[] args)
+    {
+        RunInterpreterTests();
+        return 100;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    public static void RunInterpreterTests()
+    {
+//        Console.WriteLine("Run interp tests");
+    }
+
+}

src/tests/JIT/interpreter/Interpreter.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <!-- This is a separate app launched by the actual test in InterpreterTester.csproj -->
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <ReferenceXUnitWrapperGenerator>false</ReferenceXUnitWrapperGenerator>
+    <CLRTestKind>BuildOnly</CLRTestKind>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="Interpreter.cs" />
+  </ItemGroup>
+</Project>

src/tests/JIT/interpreter/InterpreterTester.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using System.Runtime;
+using System.Text;
+
+using Xunit;
+
+public class InterpreterTester
+{
+    [Fact]
+    public static void RunTests()
+    {
+        string corerun = TestLibrary.Utilities.IsWindows ? "corerun.exe" : "corerun";
+        string libInterp = TestLibrary.Utilities.IsWindows ? "clrinterpreter.dll" : "libclrinterpreter.so";
+        string coreRoot = Environment.GetEnvironmentVariable("CORE_ROOT");
+        string interpreterApp = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "Interpreter.dll");
+
+        var startInfo = new ProcessStartInfo(Path.Combine(coreRoot, corerun), interpreterApp);
+        startInfo.EnvironmentVariables["DOTNET_AltJitName"] = libInterp;
+        startInfo.EnvironmentVariables["DOTNET_AltJitPath"] = Path.Combine(coreRoot, libInterp);
+        startInfo.EnvironmentVariables["DOTNET_AltJit"] = "RunInterpreterTests";
+
+        using (Process p = Process.Start(startInfo))
+        {
+            p.WaitForExit();
+            Console.WriteLine ("Interpreted App returned {0}", p.ExitCode);
+            if (p.ExitCode != 100)
+                throw new Exception("Interpreted App failed execution");
+        }
+    }
+}

src/tests/JIT/interpreter/InterpreterTester.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <DisableProjectBuild Condition="'$(RuntimeFlavor)' == 'Mono'">true</DisableProjectBuild>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="InterpreterTester.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="$(TestSourceDir)Common/CoreCLRTestLibrary/CoreCLRTestLibrary.csproj" />
+    <ProjectReference Include="$(MSBuildThisFileDirectory)Interpreter.csproj">
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+      <OutputItemType>Content</OutputItemType>
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </ProjectReference>
+  </ItemGroup>
+</Project>