Improve portability of build scripts

gendoc.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 (
 cat <<EOF

gents.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -euo pipefail
 
 # generate new typescript client, only install it when it is different, so we

tsc.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -euo pipefail
 
 # - todo: get tsc to not emit semicolons except for the handful cases where it is needed.