Auto merge of #3378 - micbou:visual-studio-build-tools, r=bstaletic

[READY] Instruct installing Visual Studio Build Tools 2017

As suggested by @bstaletic in https://github.com/Valloric/YouCompleteMe/issues/3376#issuecomment-485680582, Visual Studio Build Tools is sufficient to build YCM. Users are told to download the 2017 version since 2019 is not yet supported (require a change to the `build.py` script and [waiting for AppVeyor to release the image](https://github.com/appveyor/ci/issues/2907)).

Closes #3376.

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README.md

@@ -392,8 +392,8 @@ Download and install the following software:
   number exactly.
 - [CMake][cmake-download]. Add CMake executable to the PATH environment
   variable.
-- [Visual Studio][visual-studio-download]. Download the community edition.
-  During setup, select _Desktop development with C++_ in _Workloads_.
+- [Visual Studio Build Tools 2017][visual-studio-download]. During setup,
+  select _Visual C++ build tools_ in _Workloads_.
 
 Compiling YCM **with** semantic support for C-family languages through
 **libclang**:
@@ -626,8 +626,9 @@ process.
     On Windows, you need to download and install [Python 2 or
     Python 3][python-win-download]. Pick the version corresponding to your Vim
     architecture. You will also need Microsoft Visual C++ (MSVC) to build YCM.
-    You can obtain it by installing [Visual Studio][visual-studio-download].
-    MSVC 14 (Visual Studio 2015) and 15 (2017) are officially supported.
+    You can obtain it by installing [Visual Studio Build
+    Tools][visual-studio-download]. MSVC 14 (Visual Studio 2015) and 15 (2017)
+    are officially supported.
 
     Here we'll assume you installed YCM with Vundle. That means that the
     top-level YCM directory is in `~/.vim/bundle/YouCompleteMe`.
@@ -3629,7 +3630,7 @@ This software is licensed under the [GPL v3 license][gpl].
 [tsconfig.json]: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html
 [vim-win-download]: https://github.com/vim/vim-win32-installer/releases
 [python-win-download]: https://www.python.org/downloads/windows/
-[visual-studio-download]: https://www.visualstudio.com/downloads/
+[visual-studio-download]: https://visualstudio.microsoft.com/thank-you-downloading-visual-studio/?sku=BuildTools&rel=15
 [7z-download]: http://www.7-zip.org/download.html
 [mono-install-osx]: http://www.mono-project.com/docs/getting-started/install/mac/
 [mono-install-linux]: https://www.mono-project.com/download/stable/#download-lin

doc/youcompleteme.txt

@@ -600,8 +600,8 @@ Download and install the following software:
 
 - CMake [27]. Add CMake executable to the PATH environment variable.
 
-- Visual Studio [38]. Download the community edition. During setup, select
-  _Desktop development with C++_ in _Workloads_.
+- Visual Studio Build Tools 2017 [38]. During setup, select _Visual C++ build
+  tools_ in _Workloads_.
 
 Compiling YCM **with** semantic support for C-family languages through
 **libclang**:
@@ -840,8 +840,8 @@ will notify you to recompile it. You should then rerun the install process.
    On Windows, you need to download and install Python 2 or Python 3 [37].
    Pick the version corresponding to your Vim architecture. You will also
    need Microsoft Visual C++ (MSVC) to build YCM. You can obtain it by
-   installing Visual Studio [38]. MSVC 14 (Visual Studio 2015) and 15 (2017)
-   are officially supported.
+   installing Visual Studio Build Tools [38]. MSVC 14 (Visual Studio 2015)
+   and 15 (2017) are officially supported.
 
    Here we'll assume you installed YCM with Vundle. That means that the
    top-level YCM directory is in '~/.vim/bundle/YouCompleteMe'.
@@ -3884,7 +3884,7 @@ References ~
 [35] https://github.com/vim/vim-win32-installer/releases
 [36] http://vimhelp.appspot.com/starting.txt.html#vimrc
 [37] https://www.python.org/downloads/windows/
-[38] https://www.visualstudio.com/downloads/
+[38] https://visualstudio.microsoft.com/thank-you-downloading-visual-studio/?sku=BuildTools&rel=15
 [39] http://stackoverflow.com/questions/6319274/how-do-i-run-msbuild-from-the-command-line-using-windows-sdk-7-1
 [40] https://github.com/tpope/vim-pathogen#pathogenvim
 [41] http://llvm.org/releases/download.html