chore: portable bash path (#3555)

/bin/bash does not exist on some distros (e.g. NixOS). Look it up from /usr/bin/env.

Author: bclement-ocp

flambda-backend/tests/backend/vectorizer/filter.sh

@@ -1,3 +1,3 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 grep "\*\*\*\* Vectorize selected computation:" $1

jane-street-merlin-setup.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 target_dir=$PWD
 cd "$(dirname "$0")"

tools/list-globals

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
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