Auto merge of #18979 - sgift:patch-1, r=mbrubeck

Windows Build: Install Visual Studio at default location

Visual Studio 2017 has to be installed at the default location or mach.bat will show an error that Visual Studio 2017 is not installed when trying to build servo.

[X] These changes do not require tests because no code is changed, documentation only.

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README.md

@@ -111,7 +111,7 @@ pip install virtualenv
 settings for the installer are fine).
 
 4. Install Visual Studio Community 2017 (https://www.visualstudio.com/vs/community/). You MUST add "Visual C++" to the
-list of installed components. It is not on by default.
+list of installed components. It is not on by default. Visual Studio 2017 MUST installed to the default location or mach.bat will not find it.
 > If you encountered errors with the environment above, do the following for a workaround:
 > 1.  Download and install [Build Tools for Visual Studio 2017](https://www.visualstudio.com/thank-you-downloading-visual-studio/?sku=BuildTools&rel=15)
 > 2.  Install `python2.7 x86-x64` and `virtualenv`