consider updating autotool scripts

Hello, I'm from the ArchRISC-V Team, an effort to port Arch Linux to RISC-V architecture.

While porting exempi, during the configure step we experienced an error:

checking build system type... ./config.guess: unable to guess system type

This script, last modified 2009-11-20, has failed to recognize
the operating system you are using. It is advised that you
download the most up to date version of the config scripts from

  http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD
and
  http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD

If the version you run (./config.guess) is already up to date, please
send the following data and any information you think might be
pertinent to <config-patches@gnu.org> in order to provide the needed
information to handle your system.

config.guess timestamp = 2009-11-20

uname -m = riscv64
uname -r = 5.18.7-arch1-1
uname -s = Linux
uname -v = #1 SMP PREEMPT_DYNAMIC Sat, 25 Jun 2022 20:22:01 +0000

/usr/bin/uname -p = unknown
/bin/uname -X     = 

hostinfo               = 
/bin/universe          = 
/usr/bin/arch -k       = 
/bin/arch              = 
/usr/bin/oslevel       = 
/usr/convex/getsysinfo = 

UNAME_MACHINE = riscv64
UNAME_RELEASE = 5.18.7-arch1-1
UNAME_SYSTEM  = Linux
UNAME_VERSION = #1 SMP PREEMPT_DYNAMIC Sat, 25 Jun 2022 20:22:01 +0000
configure: error: cannot guess build type; you must specify one

It's been verified that running autoreconf -fiv in the project root directory resolves the problem.

We have updated our build script to run autoreconf, to make configure script updated, when packaging exempi, but as part of our duty, we do suggest our upstreams do this once and for all instead.

Thanks :)