https://github.com/sahlberg/libnfs/pull/380

From af37ac6d766755185dc023b940cfe78a176170a0 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Sun, 3 Apr 2022 04:22:04 +0100
Subject: [PATCH] autotools: fix syntax error in configure when pthreads
 disabled

Avoids this warning/syntax error in configure when pthreads aren't
enabled (default):
```
checking for special C compiler options needed for large files... no
checking for _FILE_OFFSET_BITS value needed for large files... no
./configure: 14227: test: =: unexpected operator
checking whether SO_BINDTODEVICE is available... yes
checking whether getpwnam() is available... yes
```

The LHS of the test will be blank, so use an 'x' to give a dummy
value, like we do elsewhere.

Signed-off-by: Sam James <sam@gentoo.org>
--- a/configure.ac
+++ b/configure.ac
@@ -88,7 +88,7 @@ if test x"$libnfs_cv_HAVE_PTHREAD" = x"yes"; then
     AC_DEFINE(HAVE_MULTITHREADING,1,[Whether we have multithreading support])
 fi
 fi
-AM_CONDITIONAL([HAVE_PTHREAD], [test $libnfs_cv_HAVE_PTHREAD = yes])
+AM_CONDITIONAL([HAVE_PTHREAD], [test x$libnfs_cv_HAVE_PTHREAD = xyes])
 
 AC_MSG_CHECKING(whether SO_BINDTODEVICE is available)
 AC_TRY_COMPILE([#include <net/if.h>], [