8353009: Improve documentation for Windows AArch64 builds

Reviewed-by: erikj, ihse

Author: swesonga

doc/building.html

@@ -1722,6 +1722,20 @@ <h4 id="building-for-musl">Building for musl</h4>
 --with-devkit=$DEVKIT \
 --with-sysroot=$SYSROOT</code></pre>
 <p>and run <code>make</code> normally.</p>
+<h4 id="building-for-windows-aarch64">Building for Windows AArch64</h4>
+<p>The Visual Studio Build Tools can be used for building the JDK
+without a full Visual Studio installation. To set up the Visual Studio
+2022 Build Tools on a Windows AArch64 machine for a native build, launch
+the installer as follows in a Windows command prompt:</p>
+<pre><code>vs_buildtools.exe --quiet --wait --norestart --nocache ^
+--installPath &quot;%ProgramFiles(x86)%\Microsoft Visual Studio\2022\BuildTools&quot; ^
+--add Microsoft.VisualStudio.Component.VC.CoreBuildTools ^
+--add Microsoft.VisualStudio.Component.VC.Tools.ARM64 ^
+--add Microsoft.VisualStudio.Component.Windows11SDK.22621</code></pre>
+<p>To generate Windows AArch64 builds using Cygwin on a Windows x64
+machine, you must set the proper target platform by adding
+<code>--openjdk-target=aarch64-unknown-cygwin</code> to your configure
+command line.</p>
 <h2 id="build-performance">Build Performance</h2>
 <p>Building the JDK requires a lot of horsepower. Some of the build
 tools can be adjusted to utilize more or less of resources such as

doc/building.md

@@ -1457,6 +1457,24 @@ sh ./configure --with-jvm-variants=server \
 
 and run `make` normally.
 
+#### Building for Windows AArch64
+The Visual Studio Build Tools can be used for building the JDK without a full
+Visual Studio installation. To set up the Visual Studio 2022 Build Tools on a
+Windows AArch64 machine for a native build, launch the installer as follows
+in a Windows command prompt:
+
+```
+vs_buildtools.exe --quiet --wait --norestart --nocache ^
+--installPath "%ProgramFiles(x86)%\Microsoft Visual Studio\2022\BuildTools" ^
+--add Microsoft.VisualStudio.Component.VC.CoreBuildTools ^
+--add Microsoft.VisualStudio.Component.VC.Tools.ARM64 ^
+--add Microsoft.VisualStudio.Component.Windows11SDK.22621
+```
+
+To generate Windows AArch64 builds using Cygwin on a Windows x64 machine,
+you must set the proper target platform by adding
+`--openjdk-target=aarch64-unknown-cygwin` to your configure command line.
+
 ## Build Performance
 
 Building the JDK requires a lot of horsepower. Some of the build tools can be