bug#36332: non-GUI build broken on macOS

[Paul Eggert]

Apparently Emacs master does not build in macOS when configured without a GUI, 
e.g., './configure --without-ns'. Someone with macOS experience should fix this, 
as Emacs should always be buildable without a GUI. Please see:

https://lists.gnu.org/r/emacs-devel/2019-06/msg00847.html

where Robert Pluim reports the following symptoms:

In file included from nsterm.m:49:
./nsterm.h:1322:20: error: typedef redefinition with different types
('NSUInteger' (aka 'unsigned long') vs 'enum NSWindowStyleMask')
typedef NSUInteger NSWindowStyleMask;

                   ^
/System/Library/Frameworks/AppKit.framework/Headers/NSWindow.h:35:32: note:
previous definition is here
typedef NS_OPTIONS(NSUInteger, NSWindowStyleMask) {
                               ^
In file included from nsterm.m:49:
./nsterm.h:1326:6: error: enumeration previously declared with fixed underlying
type
enum NSWindowTabbingMode
     ^