[newlib-cygwin] README: configure.in -> configure.ac

[newlib-cygwin] README: configure.in -> configure.ac

[Jon TURNEY]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=ff71c3fcdb9807fee8d9e5f898694ba56a02a013

commit ff71c3fcdb9807fee8d9e5f898694ba56a02a013
Author: Jon Turney <jon.turney@dronecode.org.uk>
Date:   Wed Dec 8 15:40:59 2021 +0000

    README: configure.in -> configure.ac
    
    These files were renamed from that long deprecated name in commit
    92061799.

Diff:
---
 newlib/README | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/newlib/README b/newlib/README
index 1c0541284..eac9f0045 100644
--- a/newlib/README
+++ b/newlib/README
@@ -545,14 +545,14 @@ $(source_dir)/src/configure --with-newlib --prefix=$(install_dir) --disable-shar
 Regenerating Configuration Files
 ================================
 
-At times you will need to make changes to configure.in and Makefile.am files.
+At times you will need to make changes to configure.ac and Makefile.am files.
 This will mean that configure and Makefile.in files will need to be
 regenerated.
 
 At the top level of newlib is the file: acinclude.m4.  This file contains
-the definition of the NEWLIB_CONFIGURE macro which is used by all configure.in
+the definition of the NEWLIB_CONFIGURE macro which is used by all configure.ac
 files in newlib.  You will notice that each directory in newlib containing
-a configure.in file also contains an aclocal.m4 file.  This file is
+a configure.ac file also contains an aclocal.m4 file.  This file is
 generated by issuing: aclocal -I${relative_path_to_toplevel_newlib_dir}
 -I${relative_path_to_toplevel_src_dir}
 The first relative directory is to access acinclude.m4.  The second relative
@@ -566,7 +566,7 @@ Note that if the top level acinclude.m4 is altered, every aclocal.m4 file
 in newlib should be regenerated.
 
 If the aclocal.m4 file is regenerated due to a change in acinclude.m4 or
-if a configure.in file is modified, the corresponding configure file in the 
+if a configure.ac file is modified, the corresponding configure file in the 
 directory must be regenerated using autoconf.  No parameters are necessary.
 In the previous example, we would issue:
 
@@ -581,12 +581,12 @@ files in newlib (and libgloss) are generated using the --cygnus option
 of automake.  
 
 Makefile.in files are generated from the nearest directory up the chain
-which contains a configure.in file.  In most cases, this is the same
-directory containing configure.in, but there are exceptions.
+which contains a configure.ac file.  In most cases, this is the same
+directory containing configure.ac, but there are exceptions.
 For example, the newlib/libc directory has a number of
-subdirectories that do not contain their own configure.in files (e.g. stdio).
+subdirectories that do not contain their own configure.ac files (e.g. stdio).
 For these directories, you must issue the automake command from newlib/libc
-which is the nearest parent directory that contains a configure.in.
+which is the nearest parent directory that contains a configure.ac.
 When you issue the automake command, you specify the subdirectory for
 the Makefile.in you are regenerating.  For example:
 
@@ -594,13 +594,13 @@ the Makefile.in you are regenerating.  For example:
 
 Note how multiple Makefile.in files can be created in the same step.  You
 would not specify machine/Makefile or sys/Makefile in the previous example
-because both of these subdirectories contain their own configure.in files.
+because both of these subdirectories contain their own configure.ac files.
 One would change to each of these subdirectories and in turn issue:
 
    automake --cygnus Makefile
 
 Let's say you create a new machine directory XXXX off of newlib/libc/machine.
-After creating a new configure.in and Makefile.am file, you would issue:
+After creating a new configure.ac and Makefile.am file, you would issue:
 
    aclocal -I ../../..
    autoconf