Patch to allow us to specify an alternate pixz binary when running tests.

This patch should be sent upstream.

--- pixz-1.0/test.sh.orig	2015-10-01 05:53:31.844847241 -0700
+++ pixz-1.0/test.sh	2015-10-01 06:03:39.267035275 -0700
@@ -3,13 +3,15 @@
 tarball=$1
 sample=$2
 
+PIXZ="${PIXZ_BIN:-./src/pixz}"
+
 echo XZ
 time xz -c < "$tarball" > test.txz
 time xz -cd < test.txz | tar xO "$sample" | md5sum
 
 echo; echo; echo PIXZ
-time ./pixz < "$tarball" > test.tpxz
-time ./pixz -x "$sample" < test.tpxz | tar xO "$sample" | md5sum
+time $PIXZ < "$tarball" > test.tpxz
+time $PIXZ -x "$sample" < test.tpxz | tar xO "$sample" | md5sum
 
 echo; echo; echo CROSS
 xz -cd < test.tpxz | tar xO "$sample" | md5sum