explicitly use bash to avoid dash compatability issues when running tests

test/basic/run.sh

-#!/bin/sh
+#!/bin/bash
 source ../lib/runner.sh

test/lex/run.sh

-#!/bin/sh
+#!/bin/bash
 NO_SEPARATE_TBS=1
 source ../lib/runner.sh

test/lib/runner.sh

-#!/bin/sh
+#!/bin/bash
 
 SCRIPT_DIR=`dirname "${BASH_SOURCE[0]}"`
 SV2V="$SCRIPT_DIR/../../bin/sv2v"

test/relong/run.sh

-#!/bin/sh
+#!/bin/bash
 source ../lib/runner.sh

test/run-all.sh

-#!/bin/sh
+#!/bin/bash
 
 cd `dirname "${BASH_SOURCE[0]}"`