windows: add ARM64 support

This was actually surprising once I got TinyGo to build on Windows 11
ARM64. All the changes are exactly what you'd expect for a new
architecture, there was no special weirdness just for arm64.

Actually getting TinyGo to build was kind of involved though. The very
short summary is: install arm64 versions of some pieces of software
(like golang, cmake) instead of installing them though choco. In
particular, use the llvm-mingw[1] toolchain instead of using standard
mingw.

[1]: https://github.com/mstorsjo/llvm-mingw/releases

builder/tools-builtin.go

@@ -28,7 +28,7 @@ const hasBuiltinTools = true
 func RunTool(tool string, args ...string) error {
 	linker := "elf"
 	if tool == "ld.lld" && len(args) >= 2 {
-		if args[0] == "-m" && args[1] == "i386pep" {
+		if args[0] == "-m" && (args[1] == "i386pep" || args[1] == "arm64pe") {
 			linker = "mingw"
 		} else if args[0] == "-flavor" {
 			linker = args[1]