multiarch: Prepare for x86_64+arm64 universal binaries in macOS 11

[Bruno Haible]

Apple announced a migration to the arm64 architecture for new Macs. Therefore
it is to be expected that there will be multi-arch ("universal") binaries in
the time of transition. Like there were during the PowerPC -> x86 transition
ca. 13 years ago.


2020-07-25  Bruno Haible  <bruno@clisp.org>

        multiarch: Prepare for x86_64+arm64 universal binaries in macOS 11.
        * m4/multiarch.m4 (gl_MULTIARCH): Recognize also the ARM architectures.

diff --git a/m4/multiarch.m4 b/m4/multiarch.m4
index 69b43df..2c61afb 100644
--- a/m4/multiarch.m4
+++ b/m4/multiarch.m4
@@ -1,4 +1,4 @@
-# multiarch.m4 serial 8
+# multiarch.m4 serial 9
 dnl Copyright (C) 2008-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -39,7 +39,7 @@ AC_DEFUN_ONCE([gl_MULTIARCH],
         for word in ${CC} ${CFLAGS} ${CPPFLAGS} ${LDFLAGS}; do
           if test -n "$prev"; then
             case $word in
-              i?86 | x86_64 | ppc | ppc64)
+              i?86 | x86_64 | ppc | ppc64 | arm | arm64)
                 if test -z "$arch" || test "$arch" = "$word"; then
                   arch="$word"
                 else