Clean shell scripts (#398)

scripts/build/client.sh

@@ -1,6 +1,8 @@
-#!/bin/bash
+#!/bin/sh
 
-cd client || exit -1
+set -eu
+
+cd client
 
 rm -rf ./dist ./compiled
 

scripts/build/server.sh

@@ -1,4 +1,6 @@
-#!/usr/bin/env sh
+#!/bin/sh
+
+set -eu
 
 rm -rf ./dist