[glom] Add comment about .DELETE_ON_ERROR: special target

[Daniel Elstner <daniel src gnome org>]

commit 1305939668c49f5cc380d38e0783ea7f37b7587f
Author: Daniel Elstner <danielk openismus com>
Date:   Thu Jul 23 21:13:07 2009 +0200

    Add comment about .DELETE_ON_ERROR: special target

 Makefile.am |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 5142795..4dd45f1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -763,4 +763,6 @@ endif
 .PHONY: install-update-icon-cache uninstall-update-icon-cache \
 	install-update-mime-database uninstall-update-mime-database
 
+# Instruct GNU make to delete the targets of a rule after it failed, in
+# order to avoid the complication of handling that situation manually.
 .DELETE_ON_ERROR: