Obtain bash path through /usr/bin/env in flow scripts.

Unfortunately, not all systems have bash in /bin. One notable example is nixos.
When entering a development shell in nixos, the current version of the scripts
will fail complaining that "something is wrong at line 1". The issue is that
there is no /bin/bash on NixOS or more generally on the system.

Author: Marco Minutoli

flow/scripts/escape.sh

@@ -1,2 +1,2 @@
-#!/bin/bash
+#!/usr/bin/env bash
 sed -e 's/ /\\ /g' -e 's/(/\\(/g' -e 's/|/\\|/g' -e 's/)/\\)/g'

flow/scripts/flow.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -u -eo pipefail
 mkdir -p $RESULTS_DIR $LOG_DIR $REPORTS_DIR $OBJECTS_DIR
 echo Running $2.tcl, stage $1

flow/scripts/synth.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -u -eo pipefail
 mkdir -p $RESULTS_DIR $LOG_DIR $REPORTS_DIR $OBJECTS_DIR
 eval "$TIME_CMD $YOSYS_EXE $YOSYS_FLAGS -c $1" 2>&1 | tee $(realpath $2)