[flang] The #! sequence must be at the start of the script file. (flang-compiler/f18#894)

Original-commit: flang-compiler/f18@b1ff232730
Reviewed-on: https://github.com/flang-compiler/f18/pull/894

flang/tools/f18/flang.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 #===-- tools/f18/flang.sh -----------------------------------------*- sh -*-===#
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -6,8 +7,6 @@
 #
 #------------------------------------------------------------------------------#
 
-#!/bin/bash
-
 function abspath() {
   pushd . > /dev/null;
   if [ -d "$1" ]; then