[newlib-cygwin] etc: rename configure.in to configure.ac

[Michael Frysinger]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=8e1bc22456f9d6e8b301613236321e6ecdb5f18e

commit 8e1bc22456f9d6e8b301613236321e6ecdb5f18e
Author: Mike Frysinger <vapier@gentoo.org>
Date:   Thu Sep 9 16:40:36 2021 -0400

    etc: rename configure.in to configure.ac
    
    The .in name has been deprecated for a long time in favor of .ac.

Diff:
---
 etc/{configure.in => configure.ac} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)

diff --git a/etc/configure.in b/etc/configure.ac
similarity index 100%
rename from etc/configure.in
rename to etc/configure.ac