Allow for bash in locations other than /bin

tcltk/ext2sim.sh.in

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Standalone script for ext2sim, for Tcl-based magic 8.0
 #

tcltk/ext2spice.sh.in

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Standalone script for ext2spice, for Tcl-based magic 8.0
 #

tcltk/magic.sh.in

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # For installation, put this file (magic.sh) in a known executable path.
 # Put startup script "magic.tcl", shared library "tclmagic.so", and