doc: building - note on Windows SDK 15063

PR-URL: #14394
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: João Reis <reis@janeasystems.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

BUILDING.md

@@ -172,7 +172,8 @@ Prerequisites:
     including the Community edition (remember to select
     "Common Tools for Visual C++ 2015" feature during installation).
   * [Visual Studio 2017](https://www.visualstudio.com/downloads/), any edition (including the Build Tools SKU).
-    **Required Components:** "MSbuild", "VC++ 2017 v141 toolset" and one of the Windows SDKs (10 or 8.1).
+    **Required Components:** "MSbuild", "VC++ 2017 v141 toolset" and at least one of the Windows SDKs.
+    *Note*: For "Windows 10 SDK (10.0.15063.0)" only the "Desktop C++ x86 and x64" flavor is required.
 * Basic Unix tools required for some tests,
   [Git for Windows](http://git-scm.com/download/win) includes Git Bash
   and tools which can be included in the global `PATH`.