(build) update mono to v6.4.0

Author: arturcic

src/GitVersionExe/ExecCommand.cs

@@ -111,7 +111,7 @@ private static string GetMsBuildToolPath()
             }
             if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
             {
-                return "/usr/local/bin/msbuild";
+                return "/Library/Frameworks/Mono.framework/Versions/Current/Commands/msbuild";
             }
             throw new Exception("MsBuild not found");
         }