packaging: Use standard strict mode header

The script already turned on `-e` later on. Make it conform to the
standard strict mode with the rest of the options right at the
beginning.

Closes: #1554
Approved by: cgwalters

packaging/make-git-snapshot.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+set -xeuo pipefail
 
 srcdir=$1
 shift
@@ -10,9 +11,6 @@ shift
 TARFILE=${PKG_VER}.tar
 TARFILE_TMP=$(pwd)/${TARFILE}.tmp
 
-set -x
-set -e
-
 test -n "${srcdir}"
 test -n "${PKG_VER}"
 test -n "${GITREV}"