https://sourceforge.net/p/sigrok/mailman/message/32459769/

From dc83770847c39934f5cbc63c8652124fafcb8d0b Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Sat, 14 Jun 2014 01:37:12 -0400
Subject: [PATCH 1/2] fix test operator

The == operator is not in POSIX.
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 9527379..3f661ec 100644
--- a/configure.ac
+++ b/configure.ac
@@ -125,7 +125,7 @@ AC_SUBST(MODNAME_PYTHON)
 # We also need to find the name of the python3 executable (for 'make install').
 # Some OSes call this python3, some call it python3.2, etc. etc.
 AC_CHECK_PROGS([PYTHON3], [python3.4 python3.3 python3.2 python3])
-if test "x$PYTHON3" == "x"; then
+if test "x$PYTHON3" = "x"; then
 	AC_MSG_ERROR([cannot find python3 executable.])
 fi
 
-- 
2.0.0