Further hardern the logic inside HostFxrResolver

Adds more logging and handles empty folder.

src/MSBuildLocator/DotNetSdkLocationHelper.cs

@@ -133,16 +133,16 @@ private static IntPtr HostFxrResolver(Assembly assembly, string libraryName)
  {
  Console.Error.WriteLine($"Try to load native library {libraryName}");
 
- var hostFxrLibName = "libhostfxr";
- var libExtension = RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "dylib" : "so";
+ string hostFxrLibName = "libhostfxr";
+ string libExtension = RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "dylib" : "so";
 
  // the DllImport hardcoded the name as hostfxr.
  if (!hostFxrLibName.Equals(libraryName, StringComparison.OrdinalIgnoreCase) && !libraryName.Equals("hostfxr", StringComparison.OrdinalIgnoreCase))
  {
  return IntPtr.Zero;
  }
 
- var hostFxrRoot = Path.Combine(DotnetPath.Value, "host", "fxr");
+ string hostFxrRoot = Path.Combine(DotnetPath.Value, "host", "fxr");
  if (Directory.Exists(hostFxrRoot))
  {
  var fileEnumerable = new FileSystemEnumerable<SemanticVersion?>(
@@ -153,16 +153,35 @@ private static IntPtr HostFxrResolver(Assembly assembly, string libraryName)
  };
 
  // Load hostfxr from the highest version, because it should be backward-compatible
- SemanticVersion? hostFxrVersion = fileEnumerable.Max();
+ SemanticVersion? hostFxrVersion;
+
+ try
+ {
+ hostFxrVersion = fileEnumerable.Max();
+ }
+ catch (ArgumentException)
+ {
+ // LINQ Max throws when the list is empty.
+ Console.Error.WriteLine($"No child folder was found in '{hostFxrRoot}'.");
+ return IntPtr.Zero;
+ }
 
  if (hostFxrVersion is not null)
  {
- var hostFxrAssembly = Path.Combine(hostFxrRoot, hostFxrVersion.OriginalValue, Path.ChangeExtension(hostFxrLibName, libExtension));
+ string hostFxrAssembly = Path.Combine(hostFxrRoot, hostFxrVersion.OriginalValue, Path.ChangeExtension(hostFxrLibName, libExtension));
 
  if (File.Exists(hostFxrAssembly))
  {
  return NativeLibrary.TryLoad(hostFxrAssembly, out var handle) ? handle : IntPtr.Zero;
  }
+ else
+ {
+ Console.Error.WriteLine($"hostfxr file '{hostFxrAssembly}' cannot be found.");
+ }
+ }
+ else
+ {
+ Console.Error.WriteLine($"No runtime version was found in '{hostFxrRoot}'.");
  }
  }
  else