Support aarch64 Windows arch in TargetTriple::from_host()

Author: Alovchin91

doc/src/installation/windows.md

@@ -16,7 +16,7 @@ tools" and "Windows 10 SDK" option. No additional software installation is
 necessary for basic use of the GNU build.
 
 By default `rustup` on Windows configures Rust to target the MSVC ABI, that is
-a target triple of either `i686-pc-windows-msvc` or `x86_64-pc-windows-msvc`
+a target triple of either `i686-pc-windows-msvc`, `x86_64-pc-windows-msvc`, or `aarch64-pc-windows-msvc`
 depending on the CPU architecture of the host Windows OS. The toolchains that
 `rustup` chooses to install, unless told otherwise through the [toolchain
 specification], will be compiled to run on that target triple host and will

src/dist/dist.rs

@@ -234,6 +234,7 @@ impl TargetTriple {
             // First detect architecture
             const PROCESSOR_ARCHITECTURE_AMD64: u16 = 9;
             const PROCESSOR_ARCHITECTURE_INTEL: u16 = 0;
+            const PROCESSOR_ARCHITECTURE_ARM64: u16 = 12;
 
             let mut sys_info;
             unsafe {
@@ -244,6 +245,7 @@ impl TargetTriple {
             let arch = match unsafe { sys_info.u.s() }.wProcessorArchitecture {
                 PROCESSOR_ARCHITECTURE_AMD64 => "x86_64",
                 PROCESSOR_ARCHITECTURE_INTEL => "i686",
+                PROCESSOR_ARCHITECTURE_ARM64 => "aarch64",
                 _ => return None,
             };