windows: document the return type mismatch for CommandLineToArgv

For golang/go#63236.

Change-Id: Id6c458e2ee2291e28685d24e86c05702d9fd132a
Cq-Include-Trybots: luci.golang.try:x_sys-gotip-windows-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/sys/+/531175
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/windows/zsyscall_windows.go b/windows/zsyscall_windows.go
index 2e193c3..8b1688d 100644
--- a/windows/zsyscall_windows.go
+++ b/windows/zsyscall_windows.go
@@ -3844,9 +3844,9 @@
 	return
 }
 
-func CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, err error) {
+func commandLineToArgv(cmd *uint16, argc *int32) (argv **uint16, err error) {
 	r0, _, e1 := syscall.Syscall(procCommandLineToArgvW.Addr(), 2, uintptr(unsafe.Pointer(cmd)), uintptr(unsafe.Pointer(argc)), 0)
-	argv = (*[8192]*[8192]uint16)(unsafe.Pointer(r0))
+	argv = (**uint16)(unsafe.Pointer(r0))
 	if argv == nil {
 		err = errnoErr(e1)
 	}