Fix libgtk2 post install hook regression

Signed-off-by: Paulius Zaleckas <paulius.zaleckas@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libgtk2/libgtk2.mk

@@ -119,7 +119,7 @@ define LIBGTK2_POST_INSTALL_TWEAKS
 	rm -rf $(TARGET_DIR)/usr/share/gtk-2.0/demo $(TARGET_DIR)/usr/bin/gtk-demo
 endef
 
-LIBGTK2_POST_INSTALL_TARGET_HOOKS += LIBGTK_POST_INSTALL_TWEAKS
+LIBGTK2_POST_INSTALL_TARGET_HOOKS += LIBGTK2_POST_INSTALL_TWEAKS
 
 # We do not build a full version of libgtk2 for the host, because that
 # requires compiling Cairo, Pango, ATK and X.org for the