Remove bashism from scripts/prepare_build.sh

scripts/prepare_build.sh

-#!/bin/bash
+#!/bin/sh
 
 retry() {
     if eval "$@"; then
@@ -24,11 +24,12 @@ if [ -f /.dockerenv ] || [ -f ./dockerinit ]; then
     cp config/resque.yml.example config/resque.yml
     sed -i 's/localhost/redis/g' config/resque.yml
 
-    export FLAGS=(--path vendor --retry 3 --quiet)
+    export FLAGS="--path vendor --retry 3 --quiet"
 else
-    export PATH=$HOME/bin:/usr/local/bin:/usr/bin:/bin
+    rnd=$(awk 'BEGIN { srand() ; printf("%d\n",rand()*5) }')
+    export PATH="$HOME/bin:/usr/local/bin:/usr/bin:/bin"
     cp config/database.yml.mysql config/database.yml
     sed "s/username\:.*$/username\: runner/" -i config/database.yml
     sed "s/password\:.*$/password\: 'password'/" -i config/database.yml
-    sed "s/gitlabhq_test/gitlabhq_test_$((RANDOM/5000))/" -i config/database.yml
+    sed "s/gitlabhq_test/gitlabhq_test_$rnd/" -i config/database.yml
 fi