Unbreak Cygwin bash igncr mode with ac_cr

[Aaron W. LaFramboise]

The addition of the ac_cr code to config.status broke running in Cygwin 
bash's igncr mode.  When run in such a mode, ./configure fails as follows.

> config.status: creating Makefile
> gawk: ./confcD5836/subs.awk:1: BEGIN {\r
> gawk: ./confcD5836/subs.awk:1:        ^ backslash not last character on line
> config.status: error: could not create Makefile


Background:

The igncr mode essentially ignores or throws away any carriage returns 
found as bash is parsing a file.  It has an effect somewhat similar to 
using Cygwin text mode mounts, and in practice, it makes a lot of 
strange line ending-related issues go away.

I know that this option may be somewhat controversial, but given that 
its the only really effective way to handle certain sorts of problems on 
Cygwin, I think it's important that autoconf be able to run under this mode.


The problem is that the ac_cr variable ends up being empty.  The recent 
change to use tr instead of a bare carriage return has no effect on this.

One way to solve this is to just skip the conversion step if igncr is 
set, which can be detected by checking for the empty ac_cr variable. 
I've attached a patch that implements this solution and seems to fix the 
problem for me.

What do you guys think about this?

2008-01-08  Aaron W. LaFramboise  <address@hidden>

        * lib/autoconf/status.m4 (ac_cr): Skip processing if empty.

Index: lib/autoconf/status.m4
===================================================================
RCS file: /srv/git/autoconf.git/HEAD/lib/autoconf/status.m4,v
retrieving revision 1.172
diff -p -u lib/autoconf/status.m4
--- lib/autoconf/status.m4 revision 1.172
+++ lib/autoconf/status.m4 working copy
@@ -558,7 +558,7 @@
 dnl unlikely if the configure script itself happens to be converted
 dnl to w32 text mode.
 cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
-if sed "s/$ac_cr//" < /dev/null > /dev/null 2>&1; then
+if test "x$ac_cr" != x && sed "s/$ac_cr//" < /dev/null > /dev/null 2>&1; then
   sed "s/$ac_cr\$//; s/$ac_cr/$ac_cs_awk_cr/g"
 else
   cat