Update config.guess and config.sub to latest versions.

Also update the policy in doc/RELEASE.md to get the latest versions at the beginning of the release cycle. The older policy was created when we were getting new versions right before the release.

doc/RELEASE.md

@@ -162,7 +162,7 @@ If so, update the version above and copy `lib/install-sh` from the `automake` re
 wget -O ${PGBR_REPO?}/src/build/install-sh '[URL]'
 ```
 
-Get the latest versions of `config.sub` and `config.guess`. These files are not versioned so only keep the version if it is at least two months old to help ensure stability.
+Get the latest versions of `config.sub` and `config.guess`. These files are not versioned so the newest version is pulled at the beginning of the release cycle to allow time to test stability.
 ```
 wget -O ${PGBR_REPO?}/src/build/config.guess 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD'
 wget -O ${PGBR_REPO?}/src/build/config.sub 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD'

src/build/config.guess

@@ -2,7 +2,7 @@
 # Attempt to guess a canonical system name.
 #   Copyright 1992-2020 Free Software Foundation, Inc.
 
-timestamp='2020-01-01'
+timestamp='2020-07-12'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -1095,7 +1095,17 @@ EOF
 	echo "$UNAME_MACHINE"-dec-linux-"$LIBC"
 	exit ;;
     x86_64:Linux:*:*)
-	echo "$UNAME_MACHINE"-pc-linux-"$LIBC"
+	set_cc_for_build
+	LIBCABI=$LIBC
+	if [ "$CC_FOR_BUILD" != no_compiler_found ]; then
+	    if (echo '#ifdef __ILP32__'; echo IS_X32; echo '#endif') | \
+		(CCOPTS="" $CC_FOR_BUILD -E - 2>/dev/null) | \
+		grep IS_X32 >/dev/null
+	    then
+		LIBCABI="$LIBC"x32
+	    fi
+	fi
+	echo "$UNAME_MACHINE"-pc-linux-"$LIBCABI"
 	exit ;;
     xtensa*:Linux:*:*)
 	echo "$UNAME_MACHINE"-unknown-linux-"$LIBC"
@@ -1332,6 +1342,9 @@ EOF
     *:Rhapsody:*:*)
 	echo "$UNAME_MACHINE"-apple-rhapsody"$UNAME_RELEASE"
 	exit ;;
+    arm64:Darwin:*:*)
+	echo aarch64-apple-darwin"$UNAME_RELEASE"
+	exit ;;
     *:Darwin:*:*)
 	UNAME_PROCESSOR=`uname -p`
 	case $UNAME_PROCESSOR in
@@ -1629,6 +1642,12 @@ copies of config.guess and config.sub with the latest versions from:
   https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess
 and
   https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub
+EOF
+
+year=`echo $timestamp | sed 's,-.*,,'`
+# shellcheck disable=SC2003
+if test "`expr "\`date +%Y\`" - "$year"`" -lt 3 ; then
+   cat >&2 <<EOF
 
 If $0 has already been updated, send the following data and any
 information you think might be pertinent to config-patches@gnu.org to
@@ -1656,6 +1675,7 @@ UNAME_RELEASE = "$UNAME_RELEASE"
 UNAME_SYSTEM  = "$UNAME_SYSTEM"
 UNAME_VERSION = "$UNAME_VERSION"
 EOF
+fi
 
 exit 1