Math.NET Numerics: 4.9.1 docs update

Build.html

@@ -212,6 +212,9 @@ these packages as well, with the following prefixes:</p>
 <p>The build expects that either Intel Parallel Studio 2020 (with the Intel Compiler)
 or Intel Math Kernel Library 2020 is installed. If you run into an error with <code>mkl_link_tool.exe</code>
 you may need to patch a targets file, see <a href="https://software.intel.com/en-us/forums/intel-math-kernel-library/topic/851578">MKL 2020.1, VS2019 linking bug </a>.</p>
+<p>The build is targeting <code>Windows 10 SDK (10.0.17763.0)</code> and the <code>v141</code> platform toolset,
+both of which can be installed as individual components in the Visual Studio Installer,
+together with the <code>Desktop development with C++</code> workload.</p>
 <p>The build can then be triggered by calling:</p>
 <table class="pre"><tr><td class="lines"><pre class="fssnip"><span class="l">1: </span>
 <span class="l">2: </span>