Not every /bin/sh is bash
--- pixz-1.0.7/test/cppcheck-src.sh.orig	2020-05-25 05:30:21.000000000 +0000
+++ pixz-1.0.7/test/cppcheck-src.sh	2020-12-03 19:07:09.528083390 +0000
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 if which cppcheck &> /dev/null ; then
   cppcheck --error-exitcode=1 $srcdir/../src