Merge pull request #2383 from barton2526/windows-build

doc: Update Windows build instructions

Author: jamescowens

doc/build-windows.md

@@ -5,11 +5,8 @@ Below are some notes on how to build Gridcoin for Windows.
 
 The options known to work for building Gridcoin on Windows are:
 
-* On Linux, using the [Mingw-w64](https://mingw-w64.org/doku.php) cross compiler tool chain. Ubuntu Bionic 18.04 is required
-and is the platform used to build the Gridcoin Windows release binaries.
-* On Windows, using [Windows
-Subsystem for Linux (WSL)](https://docs.microsoft.com/windows/wsl/about) and the Mingw-w64 cross compiler tool chain.
-* On Windows, using a native compiler tool chain such as [Visual Studio](https://www.visualstudio.com).
+* On Linux, using the [Mingw-w64](https://www.mingw-w64.org/) cross compiler tool chain.
+* On Windows, using [Windows Subsystem for Linux (WSL)](https://docs.microsoft.com/windows/wsl/about) and Mingw-w64.
 
 Other options which may work, but which have not been extensively tested are (please contribute instructions):
 
@@ -18,35 +15,7 @@ Other options which may work, but which have not been extensively tested are (pl
 Installing Windows Subsystem for Linux
 ---------------------------------------
 
-With Windows 10, Microsoft has released a new feature named the [Windows
-Subsystem for Linux (WSL)](https://docs.microsoft.com/windows/wsl/about). This
-feature allows you to run a bash shell directly on Windows in an Ubuntu-based
-environment. Within this environment you can cross compile for Windows without
-the need for a separate Linux VM or server. Note that while WSL can be installed with
-other Linux variants, such as OpenSUSE, the following instructions have only been
-tested with Ubuntu.
-
-This feature is not supported in versions of Windows prior to Windows 10 or on
-Windows Server SKUs. In addition, it is available [only for 64-bit versions of
-Windows](https://docs.microsoft.com/windows/wsl/install-win10).
-
-Full instructions to install WSL are available on the above link.
-To install WSL on Windows 10 with Fall Creators Update installed (version >= 16215.0) do the following:
-
-1. Enable the Windows Subsystem for Linux feature
-  * Open the Windows Features dialog (`OptionalFeatures.exe`)
-  * Enable 'Windows Subsystem for Linux'
-  * Click 'OK' and restart if necessary
-2. Install Ubuntu
-  * Open Microsoft Store and search for "Ubuntu 18.04" or use [this link](https://www.microsoft.com/store/productId/9N9TNGVNDL3Q)
-  * Click Install
-3. Complete Installation
-  * Open a cmd prompt and type "Ubuntu1804"
-  * Create a new UNIX user account (this is a separate account from your Windows account)
-
-After the bash shell is active, you can follow the instructions below, starting
-with the "Cross-compilation" section. Compiling the 64-bit version is
-recommended, but it is possible to compile the 32-bit version.
+Follow the upstream installation instructions, available [here](https://docs.microsoft.com/windows/wsl/install-win10).
 
 Cross-compilation for Ubuntu and Windows Subsystem for Linux
 ------------------------------------------------------------
@@ -80,9 +49,24 @@ The first step is to install the mingw-w64 cross-compilation tool chain:
 
     sudo apt install g++-mingw-w64-x86-64
 
-Ubuntu Bionic 18.04:
+Next, set the default `mingw32 g++` compiler option to POSIX:
 
-    sudo update-alternatives --config x86_64-w64-mingw32-g++ # Set the default mingw32 g++ compiler option to posix.
+```
+sudo update-alternatives --config x86_64-w64-mingw32-g++
+```
+
+After running the above command, you should see output similar to that below.
+Choose the option that ends with `posix`.
+
+```
+There are 2 choices for the alternative x86_64-w64-mingw32-g++ (providing /usr/bin/x86_64-w64-mingw32-g++).
+  Selection    Path                                   Priority   Status
+------------------------------------------------------------
+  0            /usr/bin/x86_64-w64-mingw32-g++-win32   60        auto mode
+* 1            /usr/bin/x86_64-w64-mingw32-g++-posix   30        manual mode
+  2            /usr/bin/x86_64-w64-mingw32-g++-win32   60        manual mode
+Press <enter> to keep the current choice[*], or type selection number:
+```
 
 Once the toolchain is installed the build steps are common:
 
@@ -102,9 +86,9 @@ Build using:
     cd depends
     make HOST=x86_64-w64-mingw32
     cd ..
-    ./autogen.sh # not required when building from tarball
+    ./autogen.sh
     CONFIG_SITE=$PWD/depends/x86_64-w64-mingw32/share/config.site ./configure --prefix=/
-    make
+    make # use "-j N" for N parallel jobs
     sudo bash -c "echo 1 > /proc/sys/fs/binfmt_misc/status" # Enable WSL support for Win32 applications.
 
 ## Building for 32-bit Windows
@@ -113,7 +97,7 @@ To build executables for Windows 32-bit, install the following dependencies:
 
     sudo apt-get install g++-mingw-w64-i686 mingw-w64-i686-dev 
 
-For Ubuntu Xenial 16.04, Ubuntu Zesty 17.04 and Windows Subsystem for Linux:
+Next, set the default `mingw32 g++` compiler option to POSIX:
 
     sudo update-alternatives --config i686-w64-mingw32-g++  # Set the default mingw32 g++ compiler option to posix.
 
@@ -131,9 +115,9 @@ Then build using:
     cd depends
     make HOST=i686-w64-mingw32
     cd ..
-    ./autogen.sh # not required when building from tarball
+    ./autogen.sh
     CONFIG_SITE=$PWD/depends/i686-w64-mingw32/share/config.site ./configure --prefix=/
-    make
+    make # use "-j N" for N parallel jobs
     sudo bash -c "echo 1 > /proc/sys/fs/binfmt_misc/status" # Enable WSL support for Win32 applications.
 
 ## Depends system