syscall: make mksyscall_windows.go -systemdll flag true by default

Updates #15167

Change-Id: I826f67e75011ba79325a1294ac0d70d7c6a3e32f
Reviewed-on: https://go-review.googlesource.com/23022Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/internal/syscall/windows/registry/syscall.go

@@ -8,7 +8,7 @@ package registry
 
 import "syscall"
 
-//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go -systemdll syscall.go
+//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall.go
 
 const (
 	_REG_OPTION_NON_VOLATILE = 0

src/internal/syscall/windows/syscall_windows.go

@@ -6,7 +6,7 @@ package windows
 
 import "syscall"
 
-//go:generate go run ../../../syscall/mksyscall_windows.go -output zsyscall_windows.go -systemdll syscall_windows.go
+//go:generate go run ../../../syscall/mksyscall_windows.go -output zsyscall_windows.go syscall_windows.go
 
 const GAA_FLAG_INCLUDE_PREFIX = 0x00000010
 

src/syscall/mksyscall_windows.go

@@ -68,7 +68,7 @@ import (
 var (
 	filename       = flag.String("output", "", "output file name (standard output if omitted)")
 	printTraceFlag = flag.Bool("trace", false, "generate print statement after every syscall")
-	systemDLL      = flag.Bool("systemdll", false, "whether all DLLs should be loaded from the Windows system directory")
+	systemDLL      = flag.Bool("systemdll", true, "whether all DLLs should be loaded from the Windows system directory")
 )
 
 func trim(s string) string {