Make the compiler used by Makefile.devel customizable.

Reported by Mike Fulton <mikefultonpersonal@gmail.com> in
<https://lists.gnu.org/archive/html/bug-gnu-libiconv/2023-05/msg00006.html>.

* Makefile.devel: Require GNU make.
(CC): Use value from the environment, if set and non-empty.
(CFLAGS): Use value from the environment, if set.
* autogen.sh (GMAKE): New variable.
Use it for executing Makefile.devel.

Author: bhaible

ChangeLog

@@ -1,3 +1,14 @@
+2023-05-19  Bruno Haible  <bruno@clisp.org>
+
+	Make the compiler used by Makefile.devel customizable.
+	Reported by Mike Fulton <mikefultonpersonal@gmail.com> in
+	<https://lists.gnu.org/archive/html/bug-gnu-libiconv/2023-05/msg00006.html>.
+	* Makefile.devel: Require GNU make.
+	(CC): Use value from the environment, if set and non-empty.
+	(CFLAGS): Use value from the environment, if set.
+	* autogen.sh (GMAKE): New variable.
+	Use it for executing Makefile.devel.
+
 2023-05-17  Bruno Haible  <bruno@clisp.org>
 
 	On z/OS, allow charset tagging of temporary shell scripts.

Makefile.devel

@@ -1,6 +1,13 @@
 # -*- makefile -*-
 # This is the developer's makefile, not the user's makefile.
 # Don't use it unless you know exactly what you do!
+# It requires GNU make.
+# It obeys the environment variables GNULIB_TOOL, CC, CFLAGS
+# if you have set them.
+
+ifneq (,)
+This makefile requires GNU Make.
+endif
 
 SHELL = /bin/sh
 MAKE = make
@@ -9,8 +16,26 @@ AUTOHEADER = autoheader
 AUTOMAKE = automake-1.16
 ACLOCAL = aclocal-1.16
 GPERF = gperf
-CC = gcc -Wall
+
+# Ignore the built-in default for CC. Also ignore $(CC) if it is empty.
+# https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
+# https://www.gnu.org/software/make/manual/html_node/Origin-Function.html
+# https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-findstring
+# https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-stripping-whitespace
+# https://www.gnu.org/software/make/manual/html_node/Conditional-Functions.html#index-or
+# https://www.gnu.org/software/make/manual/html_node/Override-Directive.html
+ifneq ($(or $(findstring $(origin CC), undefined default),$(if $(strip $(CC)),,empty)),)
+override CC = gcc -Wall
+endif
+
+# Ignore the built-in default for CFLAGS.
+# https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
+# https://www.gnu.org/software/make/manual/html_node/Origin-Function.html
+# https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-findstring
+ifneq ($(findstring $(origin CFLAGS), undefined default),)
 CFLAGS = -O
+endif
+
 MAN2HTML = groff -mandoc -Thtml
 CP = cp
 RM = rm -f

autogen.sh

@@ -8,7 +8,7 @@
 # It also requires
 #   - the gperf program.
 
-# Copyright (C) 2003-2012, 2016, 2018-2022 Free Software Foundation, Inc.
+# Copyright (C) 2003-2012, 2016, 2018-2023 Free Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -47,6 +47,22 @@ done
 
 # ========== Copy files from gnulib, automake, or the internet. ==========
 
+# Find GNU Make.
+if test -n "${MAKE}" && test "`${MAKE} --version 2>/dev/null | sed -e 's/ [0-9].*//' -e 1q`" = 'GNU Make'; then
+  GMAKE="${MAKE}"
+else
+  if test "`make --version 2>/dev/null | sed -e 's/ [0-9].*//' -e 1q`" = 'GNU Make'; then
+    GMAKE=make
+  else
+    if test "`gmake --version 2>/dev/null | sed -e 's/ [0-9].*//' -e 1q`" = 'GNU Make'; then
+      GMAKE=gmake
+    else
+      echo "*** - GNU Make not found" 1>&2
+      exit 1
+    fi
+  fi
+fi
+
 if test $skip_gnulib = false; then
   if test -n "$GNULIB_SRCDIR"; then
     test -d "$GNULIB_SRCDIR" || {
@@ -70,9 +86,9 @@ if test $skip_gnulib = false; then
     $GNULIB_TOOL --copy-file $file || exit $?
     chmod a+x $file || exit $?
   done
-  make -f Makefile.devel \
-       gnulib-clean srclib/Makefile.gnulib gnulib-imported-files srclib/Makefile.in \
-       GNULIB_TOOL="$GNULIB_TOOL"
+  $GMAKE -f Makefile.devel \
+         gnulib-clean srclib/Makefile.gnulib gnulib-imported-files srclib/Makefile.in \
+         GNULIB_TOOL="$GNULIB_TOOL"
 fi
 
 # Copy files into the libcharset subpackage, so that libcharset/autogen.sh
@@ -89,7 +105,7 @@ done
 
 # ========== Generate files. ==========
 
-make -f Makefile.devel totally-clean all || exit $?
+$GMAKE -f Makefile.devel totally-clean all || exit $?
 
 (cd libcharset
  ./autogen.sh || exit $?