Remove IO.Redist from GetPathToBuildToolsFile (#11270)

Avoids microsoft/azure-pipelines-tasks#20734 by directly using `File.Exists` in codepaths that didn't use `Microsoft.IO.Redist` until 642eed5 and turn out to be critical to the current implementation of AzDO MSBuild-using tasks.

Backport of bfa266d.

eng/Versions.props

@@ -2,7 +2,7 @@
 <!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the MIT license. See License.txt in the project root for full license information. -->
 <Project>
   <PropertyGroup>
-    <VersionPrefix>17.13.5</VersionPrefix>
+    <VersionPrefix>17.13.6</VersionPrefix>
     <DotNetFinalVersionKind>release</DotNetFinalVersionKind>
     <PackageValidationBaselineVersion>17.12.6</PackageValidationBaselineVersion>
     <AssemblyVersion>15.1.0.0</AssemblyVersion>

src/Shared/FrameworkLocationHelper.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
@@ -1390,10 +1390,11 @@ public virtual string GetPathToDotNetFramework(DotNetFrameworkArchitecture archi
                 // Assume if either MSBuild.exe or Microsoft.Build.dll are shipped, there is a valid install.
                 // Note: net481 did not ship an ARM64 MSBuild.exe, so checking its dll's is the fallback for a valid install.
                 // Context: https://github.com/dotnet/msbuild/pull/7689
+                // Rollback see https://developercommunity.visualstudio.com/t/Unable-to-locate-MSBuild-path-with-Lates/10824132 
                 if (this._hasMsBuild &&
                     generatedPathToDotNetFramework != null &&
-                    (!FileSystems.Default.FileExists(Path.Combine(generatedPathToDotNetFramework, NativeMethodsShared.IsWindows ? "MSBuild.exe" : "mcs.exe")) &&
-                     !FileSystems.Default.FileExists(Path.Combine(generatedPathToDotNetFramework, "Microsoft.Build.dll"))))
+                    (!File.Exists(Path.Combine(generatedPathToDotNetFramework, NativeMethodsShared.IsWindows ? "MSBuild.exe" : "mcs.exe")) &&
+                     !File.Exists(Path.Combine(generatedPathToDotNetFramework, "Microsoft.Build.dll"))))
                 {
                     return null;
                 }

src/Utilities/ToolLocationHelper.cs

@@ -3584,7 +3584,8 @@ public static string GetPathToBuildToolsFile(string fileName, string toolsVersio
             {
                 toolPath = Path.Combine(toolPath, fileName);
 
-                if (!FileSystems.Default.FileExists(toolPath))
+                // Rollback see https://developercommunity.visualstudio.com/t/Unable-to-locate-MSBuild-path-with-Lates/10824132 
+                if (!File.Exists(toolPath))
                 {
                     toolPath = null;
                 }