(GH-148) Update GitVersion.Tool to 5.12.0

* fixes #148

Author: devlead

build.cake

@@ -2,7 +2,7 @@
 #tool nuget:?package=NUnit.ConsoleRunner&version=3.4.0
 
 // Install .NET Core Global tools.
-#tool "dotnet:?package=GitVersion.Tool&version=5.9.0"
+#tool dotnet:?package=GitVersion.Tool&version=5.12.0
 
 ///////////////////////////////////////////////////////////////////////////////
 // ARGUMENTS