configure on riscv64 works with updated posix/config.guess and posix/config.sub

[sanderjo]

closes #755

posix/config.guess and posix/config.sub are from:

wget 'http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD' -O posix/config.guess
wget 'http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD' -O posix/config.sub

Previous posix/config.guess and posix/config.sub were from 2014 ...

[sanderjo]

@hugbug are you willing to accept this PR?

[sanderjo]

@hugbug bumping this PR.

Reason: I've got a hardware RISC-V machine now, and the git-version of nzbget fails on the ./configure:

sipeed@sipeed:~/git/nzbget$ ./configure
checking build system type... posix/config.guess: unable to guess system type

This script, last modified 2014-11-04, 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 (posix/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 = 2014-11-04

uname -m = riscv64
uname -r = 5.4.61
uname -s = Linux
uname -v = #217 PREEMPT Thu Dec 30 06:50:31 UTC 2021

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

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

UNAME_MACHINE = riscv64
UNAME_RELEASE = 5.4.61
UNAME_SYSTEM  = Linux
UNAME_VERSION = #217 PREEMPT Thu Dec 30 06:50:31 UTC 2021
configure: error: cannot guess build type; you must specify one
sipeed@sipeed:~/git/nzbget$