scripts/tags.sh: collect compiled source precisely

scripts/tags.sh: collect compiled source precisely

Parse compiled source from *.cmd but don't 'find' too many files that are
not related to compilation.

[xujialu@vimux.org: don't expand symlinks by add option -s for realpath]
Link: http://lkml.kernel.org/r/5efc5bfb.1c69fb81.41bf5.7131SMTPIN_ADDED_MISSING@mx.google.com
Signed-off-by: Jialu Xu <xujialu@vimux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joe Perches <joe@perches.com>
Link: http://lkml.kernel.org/r/5ee5d8e3.1c69fb81.9b804.47b2SMTPIN_ADDED_MISSING@mx.google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>