8379499: [AIX] headless-only build of libjawt.so fails

Backport-of: 4d42ce2

Author: MBaesken

make/modules/java.desktop/lib/AwtLibraries.gmk

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2026, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -423,6 +423,9 @@ endif
 ifeq ($(call isTargetOs, linux)+$(ENABLE_HEADLESS_ONLY), true+true)
   LIBJAWT_CFLAGS += -DHEADLESS
 endif
+ifeq ($(call isTargetOs, aix)+$(ENABLE_HEADLESS_ONLY), true+true)
+  LIBJAWT_CFLAGS += -DHEADLESS
+endif
 
 ifeq ($(call isTargetOs, windows)+$(call isTargetCpu, x86), true+true)
   LIBJAWT_LIBS_windows := kernel32.lib