[PATCH] Fix spurious error on TAGS target when missing defconfig

Not all architectures have a file named 'defconfig' (e.g.  powerpc).
However the make TAGS and make tags targets search such files for tags,
causing an error message when they don't exist.  This patch addresses the
problem by instructing xargs not to run the tags program if there are no
matching files.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -1321,7 +1321,7 @@ define xtags
 		--langdef=kconfig \
 		--language-force=kconfig \
 		--regex-kconfig='/^[[:blank:]]*config[[:blank:]]+([[:alnum:]_]+)/\1/'; \
-	    $(all-defconfigs) | xargs $1 -a \
+	    $(all-defconfigs) | xargs -r $1 -a \
 		--langdef=dotconfig \
 		--language-force=dotconfig \
 		--regex-dotconfig='/^#?[[:blank:]]*(CONFIG_[[:alnum:]_]+)/\1/'; \
@@ -1329,7 +1329,7 @@ define xtags
 	    $(all-sources) | xargs $1 -a; \
 	    $(all-kconfigs) | xargs $1 -a \
 		--regex='/^[ \t]*config[ \t]+\([a-zA-Z0-9_]+\)/\1/'; \
-	    $(all-defconfigs) | xargs $1 -a \
+	    $(all-defconfigs) | xargs -r $1 -a \
 		--regex='/^#?[ \t]?\(CONFIG_[a-zA-Z0-9_]+\)/\1/'; \
 	else \
 	    $(all-sources) | xargs $1 -a; \