minor Makefile changes

Changes #! lines in Makefiles to "#!/usr/bin/env make".

Set SHELL in Makefiles to the basename of the shell.

Makefile.simple

@@ -1,8 +1,8 @@
-#!/bin/make
+#!/usr/bin/env make
 #
 # calc - arbitrary precision calculator
 #
-# Copyright (C) 1999-2018,2021,2022  Landon Curt Noll
+# Copyright (C) 1999-2018,2021-2023  Landon Curt Noll
 #
 # SRC: Makefile.simple - non-GNU version
 #
@@ -37,7 +37,24 @@
 #
 
 
+
+# Unfortunately due to the complex dependency issues between
+# Makefile, Makefile.ship and custom/Makefile, parallel GNU make
+# is NOT recommended.  Sorry.
 #
+# XXX - fix this - XXX
+#
+.NOTPARALLEL:
+
+##############################################################################
+#-=-=-=-=-=-=-=-=- Identify the target machine, if possible -=-=-=-=-=-=-=-=-#
+##############################################################################
+
+# NOTE: You can force a target value by defining target as in:
+#
+#	make ...__optional_arguments_... target=value
+#
+
 # The shell used by this Makefile
 #
 # On some systems, /bin/sh is a rather reduced shell with
@@ -46,17 +63,18 @@
 # If your system has a up to date, bash shell, then
 # you may wish to use:
 #
-#	SHELL= /bin/bash
+#	SHELL= bash
 #
 # On some systems such as macOS, the bash shell is very
 # far behind to the point where is cannot be depended on.
 # On such systems, the sh may be a much better alternative
 # shell for this Makefile to use:
 #
-#	SHELL= /bin/sh
+#	SHELL= sh
 #
-SHELL= /bin/bash
-#SHELL= /bin/sh
+SHELL= bash
+#SHELL= sh
+
 
 ##############################################################################
 #-=-=-=-=-=-=-=-=- You may want to change some values below -=-=-=-=-=-=-=-=-#