use portable awk scripts

[Ralf Wildenhues]

Hello,

Well, `for (key in array)' is not portable awk if array is empty.  This
fixes it.  The question is whether we should now go back to using plain
awk instead of $(AWK) now and drop the dependency upon AC_PROG_AWK.
I fear it may uncover bugs in user code that just assumed AC_PROG_AWK,
so I haven't done it for now.

Anyway, I've applied this to master.

Cheers,
Ralf

    * lib/am/tags.am (ID, TAGS, CTAGS): Make awk scripts portable again.
    (CTAGS): Drop unneeded variable `here'.

diff --git a/lib/am/tags.am b/lib/am/tags.am
index 92eafd5..b3cfe6f 100644
--- a/lib/am/tags.am
+++ b/lib/am/tags.am
@@ -1,6 +1,6 @@
 ## automake - create Makefile.in from Makefile.am
-## Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004
-## Free Software Foundation, Inc.
+## Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2003,
+## 2004, 2007  Free Software Foundation, Inc.
 
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -28,8 +28,8 @@ ID: $(HEADERS) $(SOURCES) $(LISP) $(TAGS_FILES)
 ## Handle VPATH correctly.
            if test -f "$$i"; then echo $$i; else echo $(srcdir)/$$i; fi; \
          done | \
-         $(AWK) '    { files[$$0] = 1; } \
-              END { for (i in files) print i; }'`; \
+         $(AWK) '{ files[$$0] = 1; nonemtpy = 1; } \
+             END { if (nonempty) { for (i in files) print i; }; }'`; \
        mkid -fID $$unique
 
 
@@ -73,8 +73,8 @@ TAGS: %TAGSDIRS% $(HEADERS) $(SOURCES) %CONFIG% 
$(TAGS_DEPENDENCIES) \
 ## Handle VPATH correctly.
            if test -f "$$i"; then echo $$i; else echo $(srcdir)/$$i; fi; \
          done | \
-         $(AWK) '    { files[$$0] = 1; } \
-              END { for (i in files) print i; }'`; \
+         $(AWK) '{ files[$$0] = 1; nonempty = 1; } \
+             END { if (nonempty) { for (i in files) print i; }; }'`; \
 ## Make sure we have something to run etags on.
        if test -z "$(ETAGS_ARGS)$$tags$$unique"; then :; else \
          test -n "$$unique" || unique=$$empty_fix; \
@@ -97,15 +97,14 @@ ctags: CTAGS
 CTAGS: %CTAGSDIRS% $(HEADERS) $(SOURCES) %CONFIG% $(TAGS_DEPENDENCIES) \
                $(TAGS_FILES) $(LISP)
        tags=; \
-       here=`pwd`; \
 ## Make sure the list of sources is unique.
        list='$(SOURCES) $(HEADERS) %CONFIG% $(LISP) $(TAGS_FILES)'; \
        unique=`for i in $$list; do \
 ## Handle VPATH correctly.
            if test -f "$$i"; then echo $$i; else echo $(srcdir)/$$i; fi; \
          done | \
-         $(AWK) '    { files[$$0] = 1; } \
-              END { for (i in files) print i; }'`; \
+         $(AWK) '{ files[$$0] = 1; nonempty = 1; } \
+             END { if (nonempty) { for (i in files) print i; }; }'`; \
 ## Make sure we have something to run ctags on.
        test -z "$(CTAGS_ARGS)$$tags$$unique" \
          || $(CTAGS) $(CTAGSFLAGS) $(AM_CTAGSFLAGS) $(CTAGS_ARGS) \