[PATCH] Makefile: fix error when gen TAGS

[Yang Bai <hamo.by@gmail.com>]

scripts/tags.sh has a problem that it does not
test which kind of tags we are generating and
assumes tags. So when gen TAGS it shows:
  GEN     TAGS
  sed: can't read tags: No such file or directory
  make: *** [TAGS] Error 2

Signed-off-by: Yang Bai <hamo.by@gmail.com>
---
 scripts/tags.sh |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/scripts/tags.sh b/scripts/tags.sh
index 833813a..ce94e34 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -168,7 +168,11 @@ exuberant()
 	--regex-dotconfig='/^#?[[:blank:]]*(CONFIG_[[:alnum:]_]+)/\1/'
 
 	# Remove structure forward declarations.
-	LANG=C sed -i -e '/^\([a-zA-Z_][a-zA-Z0-9_]*\)\t.*\t\/\^struct \1;.*\$\/;"\tx$/d' tags
+	if [[ -e tags ]]; then
+	    LANG=C sed -i -e '/^\([a-zA-Z_][a-zA-Z0-9_]*\)\t.*\t\/\^struct \1;.*\$\/;"\tx$/d' tags
+	else
+	    LANG=C sed -i -e '/^\([a-zA-Z_][a-zA-Z0-9_]*\)\t.*\t\/\^struct \1;.*\$\/;"\tx$/d' TAGS
+	fi
 }
 
 emacs()
-- 
1.7.9.1