fix build that fails on macOS lower than 10.13 after 8214578

Change 8214578 introduced a dependency to 10.13. (NSTextInputSourceIdentifier ).

The doc of NSTextInputSourceIdentifier : https://developer.apple.com/documentation/appkit/nstextinputsourceidentifier

mentions macOS 10.13+ .

 Build errors are :
 ----------------------------

> /jdk/src/java.desktop/macosx/native/libawt_lwawt/awt/AWTView.h:41:5: error: unknown type name 'NSTextInputSourceIdentifier'
> NSTextInputSourceIdentifier kbdLayout;
> ^
> /jdk/src/java.desktop/macosx/native/libawt_lwawt/awt/AWTView.m:93:23: error: assignment to readonly property
> self.cglLayer = windowLayer;
> ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~
> /jdk/src/java.desktop/macosx/native/libawt_lwawt/awt/AWTView.m:110:19: error: assignment to readonly property
> self.cglLayer = nil;
> ~~~~~~~~~~~~~ ^ ~~~
> 3 errors generated.