8025673: [macosx] Disable X11 AWT toolkit

Summary: Disable but not completely remove the XAWT and headless toolkits on Mac OS X
Reviewed-by: dholmes
Contributed-by: david.dehaven@oracle.com

src/os/bsd/vm/os_bsd.cpp

@@ -4746,6 +4746,10 @@ int os::fork_and_exec(char* cmd) {
 // as libawt.so, and renamed libawt_xawt.so
 //
 bool os::is_headless_jre() {
+#ifdef __APPLE__
+    // We no longer build headless-only on Mac OS X
+    return false;
+#else
     struct stat statbuf;
     char buf[MAXPATHLEN];
     char libmawtpath[MAXPATHLEN];
@@ -4777,6 +4781,7 @@ bool os::is_headless_jre() {
     if (::stat(libmawtpath, &statbuf) == 0) return false;
 
     return true;
+#endif
 }
 
 // Get the default path to the core file