Cake.Common.Tools.MSBuild cant resolve VS path on pre-release

### What You Are Seeing?
Cake.Core.CakeException: MSBuild: Could not locate executable.

### What is Expected?
Be able to set `ToolVersion = MSBuildToolVersion.VS2019PreRelease`

### What version of Cake are you using?
0.34.1

### Are you running on a 32 or 64 bit system?
64

### What environment are you running on? Windows? Linux? Mac?
Windows

### Are you running on a CI Server? If so, which one?
?

### How Did You Get This To Happen? (Steps to Reproduce)

### Output Log
```
An error occurred when executing task 'libs'.
Error: System.AggregateException: One or more errors occurred. ---> Cake.Core.CakeException: MSBuild: Could not locate executable.
at Cake.Core.Tooling.Tool`1.RunProcess(TSettings settings, ProcessArgumentBuilder arguments, ProcessSettings processSettings)
at Cake.Core.Tooling.Tool`1.Run(TSettings settings, ProcessArgumentBuilder arguments, ProcessSettings processSettings, Action`1 postAction)
at Cake.Common.Tools.MSBuild.MSBuildAliases.MSBuild(ICakeContext context, FilePath solution, MSBuildSettings settings)
at Submission#0.MSBuild(FilePath solution, Action`1 configurator)
at Submission#0.<>b__0_2()
at Cake.Core.CakeTaskBuilderExtensions.<>c__DisplayClass24_0.b__0(ICakeContext x)
at Cake.Core.CakeTask.d__43.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.DefaultExecutionStrategy.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.CakeEngine.d__31.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.CakeEngine.d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Cake.Core.CakeEngine.d__27.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Scripting.BuildScriptHost.d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.Scripting.ScriptHost.RunTarget(String target)
at Submission#0.<>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.CodeAnalysis.Scripting.ScriptExecutionState.d__9`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.CodeAnalysis.Scripting.Script`1.d__21.MoveNext()
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at Cake.Scripting.Roslyn.RoslynScriptSession.Execute(Script script)
at Cake.Core.Scripting.ScriptRunner.Run(IScriptHost host, FilePath scriptPath, IDictionary`2 arguments)
at Cake.Commands.BuildCommand.Execute(CakeOptions options)
at Cake.CakeApplication.Run(CakeOptions options)
at Cake.Program.Main()
---> (Inner Exception #0) Cake.Core.CakeException: MSBuild: Could not locate executable.
at Cake.Core.Tooling.Tool`1.RunProcess(TSettings settings, ProcessArgumentBuilder arguments, ProcessSettings processSettings)
at Cake.Core.Tooling.Tool`1.Run(TSettings settings, ProcessArgumentBuilder arguments, ProcessSettings processSettings, Action`1 postAction)
at Cake.Common.Tools.MSBuild.MSBuildAliases.MSBuild(ICakeContext context, FilePath solution, MSBuildSettings settings)
at Submission#0.MSBuild(FilePath solution, Action`1 configurator)
at Submission#0.<>b__0_2()
at Cake.Core.CakeTaskBuilderExtensions.<>c__DisplayClass24_0.b__0(ICakeContext x)
at Cake.Core.CakeTask.d__43.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.DefaultExecutionStrategy.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.CakeEngine.d__31.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.CakeEngine.d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Cake.Core.CakeEngine.d__27.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Scripting.BuildScriptHost.d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Cake.Core.Scripting.ScriptHost.RunTarget(String target)
at Submission#0.<>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.CodeAnalysis.Scripting.ScriptExecutionState.d__9`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.CodeAnalysis.Scripting.Script`1.d__21.MoveNext()<---
```

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OR

~~~sh
PLACE LOG CONTENT HERE
~~~

Start at Cake.Common.Tools.MSBuild.MSBuildAliases.MSBuild and reproduce the failure on 64-bit Windows with Cake 0.34.1 and MSBuildToolVersion.VS2019PreRelease. Investigate how the MSBuild executable is located for that version; done means the setting resolves the executable instead of raising “MSBuild: Could not locate executable.”

Written by the indexing model from the issue text.