Change makexpi shebang

MB · MB · commit deda09426a9d · 2014-10-07T18:41:31.000Z
iirc, pipefail is a relic from when sh was used to build rulesets.xml.
Regardless, it isn't posixy and doesn't seem to be required.
diff --git a/makexpi.sh b/makexpi.sh
@@ -1,5 +1,5 @@
-#!/bin/bash
-set -o errexit -o pipefail
+#!/bin/sh
+set -o errexit
 APP_NAME=https-everywhere
 
 # builds a .xpi from the git repository, placing the .xpi in the root
