Pick the Arm64 rustup and Qt builds on Arm64 Windows

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

seediso/windows11/40-Install-Rustup.bat

@@ -7,8 +7,17 @@ rem The default msvc toolchain needs the MSVC Build Tools (see 20-Install-MSVC-A
 
 set "INSTALLER=%TEMP%\rustup-init.exe"
 
-echo Downloading rustup-init...
-curl.exe -L --fail -o "%INSTALLER%" https://win.rustup.rs/x86_64
+rem PROCESSOR_ARCHITEW6432 holds the real architecture when this runs under emulation.
+set "ARCH=%PROCESSOR_ARCHITECTURE%"
+if defined PROCESSOR_ARCHITEW6432 set "ARCH=%PROCESSOR_ARCHITEW6432%"
+if /i "%ARCH%"=="ARM64" (
+    set "RUSTUP_ARCH=aarch64"
+) else (
+    set "RUSTUP_ARCH=x86_64"
+)
+
+echo Downloading rustup-init (%RUSTUP_ARCH%)...
+curl.exe -L --fail -o "%INSTALLER%" https://win.rustup.rs/%RUSTUP_ARCH%
 if errorlevel 1 (
     echo Download failed.
     pause