runtime: add Windows vectored exception handler for recoverable panics

Register a vectored exception handler at startup so Windows hardware
exceptions can be translated into Go panics. Access violations become
nil pointer panics, and integer divide-by-zero exceptions become divide
by zero panics, allowing defer/recover to handle them like ordinary
runtime panics.

compileopts/target.go

@@ -485,6 +485,8 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 			"--no-insert-timestamp",
 			"--no-dynamicbase",
 		)
+		spec.ExtraFiles = append(spec.ExtraFiles,
+			"src/runtime/runtime_windows.c")
 	case "wasm", "wasip1", "wasip2":
 		return nil, fmt.Errorf("GOOS=%s but GOARCH is unset. Please set GOARCH to wasm", options.GOOS)
 	default: