Removing DotnetHostPath and setting CscToolExe to determine which script to use to run csc.exe using dotnet. Need to add the script counterpart for windows still. Doing that next.

src/dotnet/commands/dotnet-msbuild/MSBuildForwardingApp.cs

@@ -32,20 +32,21 @@ namespace Microsoft.DotNet.Tools.MSBuild
             return new Dictionary<string, string>
             {
                 { "MSBuildExtensionsPath", AppContext.BaseDirectory },
-                { "DotnetHostPath", GetHostPath() },
+                { "CscToolExe", GetRunCscPath() }
             };
         }
 
-        private static string GetHostPath()
-        {
-            return new Muxer().MuxerPath;
-        }
-
         private static string GetMSBuildExePath()
         {
             return Path.Combine(
                 AppContext.BaseDirectory,
                 s_msbuildExeName);
         }
+
+        private static string GetRunCscPath()
+        {
+            var scriptExtension = RuntimeEnvironment.OperatingSystemPlatform == Platform.Windows ? ".cmd" : ".sh";
+            return Path.Combine(AppContext.BaseDirectory, $"RunCsc{scriptExtension}");
+        }
     }
 }

src/redist/RunCsc.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) .NET Foundation and contributors. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+#
+
+set -e
+
+SOURCE="${BASH_SOURCE[0]}"
+while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
+  DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
+  SOURCE="$(readlink "$SOURCE")"
+  [[ "$SOURCE" != /* ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
+done
+DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
+
+$DIR/../../dotnet $DIR/csc.exe $@

src/redist/project.json

@@ -1,7 +1,13 @@
 {
   "version": "1.0.0-preview3-*",
   "buildOptions": {
-    "emitEntryPoint": true
+    "emitEntryPoint": true,
+    "copyToOutput": {
+      "include": "RunCsc.sh"
+    }
+  },
+  "publishOptions": {
+    "include": "RunCsc.sh"
   },
   "dependencies": {
     "Microsoft.NETCore.App": {
@@ -19,6 +25,7 @@
     "Microsoft.Build.Utilities.Core": "0.1.0-preview-00039-160922",
     "Microsoft.Build.Targets": "0.1.0-preview-00039-160922",
     "Microsoft.Build": "0.1.0-preview-00039-160922",
+    "Microsoft.CodeAnalysis.Build.Tasks": "2.0.0-beta6-60920-07",
     "System.Runtime.Serialization.Xml": "4.1.1",
     "NuGet.Build.Tasks": "3.6.0-beta.1.msbuild.9",
     "Microsoft.TestPlatform.CLI": "15.0.0-preview-20160915-01"

src/tool_msbuild/project.json

@@ -14,7 +14,7 @@
     "Microsoft.CodeAnalysis.Build.Tasks": "2.0.0-beta6-60920-07",
     "Microsoft.Cci": "4.0.0-rc3-24128-00",
     "Microsoft.Composition": "1.0.30",
-    "Microsoft.NuGet.Build.Tasks": "1.0.0-alpha-000002"
+    "Microsoft.NuGet.Build.Tasks": "1.0.0-alpha-000003"
   },
   "frameworks": {
     "netcoreapp1.0": {