[java-atk-wrapper] Warn on JNI_OnUnload getting called

[Samuel Thibault <sthibaul src gnome org>]

commit 2d1eaad996148be1a7e6ad8453529b291c2daf70
Author: Samuel Thibault <samuel thibault ens-lyon org>
Date:   Tue Jun 18 00:34:57 2019 +0200

    Warn on JNI_OnUnload getting called

 jni/src/jawutil.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/jni/src/jawutil.c b/jni/src/jawutil.c
index 3c41fea..eb023ec 100644
--- a/jni/src/jawutil.c
+++ b/jni/src/jawutil.c
@@ -327,7 +327,9 @@ JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *jvm, void *reserve)
   return JNI_VERSION_1_6;
 }
 
-JNIEXPORT void JNICALL JNI_OnUnload(JavaVM *jvm, void *reserve) {
+JNIEXPORT void JNICALL JNI_OnUnload(JavaVM *jvm, void *reserve)
+{
+  g_warning("JNI_OnUnload() called but this is not supported yet\n");
 }
 
 JNIEnv*