Use a more generic form

samples/certs/clientA.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -sha256 -keyout clientAkey.pem -out clientAreq.pem \
   -nodes -config ./clientA.cnf -days 365 -batch

samples/certs/clientB.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -sha256 -keyout clientBkey.pem -out clientBreq.pem \
   -nodes -config ./clientB.cnf -days 365 -batch

samples/certs/rootA.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -sha256 -keyout rootAkey.pem -out rootAreq.pem -nodes -config ./rootA.cnf -days 365 -batch
 

samples/certs/rootB.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -sha256 -keyout rootBkey.pem -out rootBreq.pem -nodes -config ./rootB.cnf -days 365 -batch
 

samples/certs/serverA.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -keyout serverAkey.pem -out serverAreq.pem \
    -config ./serverA.cnf -nodes -days 365 -batch

samples/certs/serverB.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 openssl req -newkey rsa:2048 -keyout serverBkey.pem -out serverBreq.pem \
    -config ./serverB.cnf -nodes -days 365 -batch