Merge pull request #8176 from jasonmalinowski/fix-finding-of-default.win32manifest

Pass Version46 to ToolLocationHelper to find default.win32manifest

src/Compilers/Core/MSBuildTask/Shared/ManagedCompiler.cs

@@ -984,7 +984,18 @@ string win32Manifest
                         string pathToDefaultManifest = ToolLocationHelper.GetPathToDotNetFrameworkFile
                                                        (
                                                            "default.win32manifest",
-                                                           TargetDotNetFrameworkVersion.VersionLatest
+
+                                                           // We are choosing to pass Version46 instead of VersionLatest. TargetDotNetFrameworkVersion
+                                                           // is an enum, and VersionLatest is not some sentinel value but rather a constant that is
+                                                           // equal to the highest version defined in the enum. Enum values, being constants, are baked
+                                                           // into consuming assembly, so specifying VersionLatest means not the latest version wherever
+                                                           // this code is running, but rather the latest version of the framework according to the
+                                                           // reference assembly with which this assembly was built. As of this writing, we are building
+                                                           // our bits on machines with Visual Studio 2015 that know about 4.6.1, so specifying
+                                                           // VersionLatest would bake in the enum value for 4.6.1. But we need to run on machines with
+                                                           // MSBuild that only know about Version46 (and no higher), so VersionLatest will fail there.
+                                                           // Explicitly passing Version46 prevents this problem.
+                                                           TargetDotNetFrameworkVersion.Version46
                                                        );
 
                         if (null == pathToDefaultManifest)