make3: Switch to env-style shebang

Much ink has been spilled over the "correct" shebang. Here, opting for
env-style is making a declaration of *intent*: These scripts prioritize
environment flexiblity over execution precision.

In particular, using a `#!/bin/sh` shebang declares that this script
shall be run by the interpreter sitting at the absolute path `/bin/sh`.
This style of shebang is useful when needing precise control over the
executing interpreter.

However, the use case for these scripts means that we have little a
priori control over the executing interpreter, and there are legitimate
cases where users may wish to use some other shell in preference to
`/bin/sh`, e.g. containerized environments. The `#!/usr/bin/env sh`
shebang caters to these needs.

Of course, there are some cases (quite rare, now) where the env-shebang
in this commit will fail [0]; however, we make the decision to
de-prioritize these cases over the aforementioned ones.

[0]:https://www.in-ulm.de/~mascheck/various/shebang/#env

Author: B. Wilson

make3/build_all.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 # build all binaries
 
 realpath()

make3/build_jconsole.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 realpath()
 {

make3/build_jnative.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 realpath()
 {

make3/build_libj.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 realpath()
 {

make3/build_tsdll.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 realpath()
 {

make3/clean.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 # rm all *.o for clean builds - makefile dependencies are not set
 
 realpath()

make3/cpbin.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 # copy binaries in bin/ to jlibrary/bin