configure.ac: Use autoconf macro for GNU make.
diff --git a/configure.ac b/configure.ac
index 1d4a6ae..f36098d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -53,7 +53,7 @@
AC_PROG_CXX
AM_PROG_CC_C_O
AM_PROG_AS
-AC_CHECK_PROGS([MAKE], [gmake make])
+AX_CHECK_GNU_MAKE
AC_CHECK_PROGS([PYTHON2], [python2 python])
AC_PROG_SED
AC_PROG_MKDIR_P
diff --git a/m4/ax_check_gnu_make.m4 b/m4/ax_check_gnu_make.m4
new file mode 100644
index 0000000..938aad7
--- /dev/null
+++ b/m4/ax_check_gnu_make.m4
@@ -0,0 +1,78 @@
+# ===========================================================================
+# http://www.gnu.org/software/autoconf-archive/ax_check_gnu_make.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_CHECK_GNU_MAKE()
+#
+# DESCRIPTION
+#
+# This macro searches for a GNU version of make. If a match is found, the
+# makefile variable `ifGNUmake' is set to the empty string, otherwise it
+# is set to "#". This is useful for including a special features in a
+# Makefile, which cannot be handled by other versions of make. The
+# variable _cv_gnu_make_command is set to the command to invoke GNU make
+# if it exists, the empty string otherwise.
+#
+# Here is an example of its use:
+#
+# Makefile.in might contain:
+#
+# # A failsafe way of putting a dependency rule into a makefile
+# $(DEPEND):
+# $(CC) -MM $(srcdir)/*.c > $(DEPEND)
+#
+# @ifGNUmake@ ifeq ($(DEPEND),$(wildcard $(DEPEND)))
+# @ifGNUmake@ include $(DEPEND)
+# @ifGNUmake@ endif
+#
+# Then configure.in would normally contain:
+#
+# AX_CHECK_GNU_MAKE()
+# AC_OUTPUT(Makefile)
+#
+# Then perhaps to cause gnu make to override any other make, we could do
+# something like this (note that GNU make always looks for GNUmakefile
+# first):
+#
+# if ! test x$_cv_gnu_make_command = x ; then
+# mv Makefile GNUmakefile
+# echo .DEFAULT: > Makefile ;
+# echo \ $_cv_gnu_make_command \$@ >> Makefile;
+# fi
+#
+# Then, if any (well almost any) other make is called, and GNU make also
+# exists, then the other make wraps the GNU make.
+#
+# LICENSE
+#
+# Copyright (c) 2008 John Darrington <j.darrington@elvis.murdoch.edu.au>
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice
+# and this notice are preserved. This file is offered as-is, without any
+# warranty.
+
+#serial 7
+
+AC_DEFUN([AX_CHECK_GNU_MAKE], [ AC_CACHE_CHECK( for GNU make,_cv_gnu_make_command,
+ _cv_gnu_make_command='' ;
+dnl Search all the common names for GNU make
+ for a in "$MAKE" make gmake gnumake ; do
+ if test -z "$a" ; then continue ; fi ;
+ if ( sh -c "$a --version" 2> /dev/null | grep GNU 2>&1 > /dev/null ) ; then
+ _cv_gnu_make_command=$a ;
+ break;
+ fi
+ done ;
+ ) ;
+dnl If there was a GNU version, then set @ifGNUmake@ to the empty string, '#' otherwise
+ if test "x$_cv_gnu_make_command" != "x" ; then
+ ifGNUmake='' ;
+ else
+ ifGNUmake='#' ;
+ AC_MSG_RESULT("Not found");
+ fi
+ AC_SUBST(ifGNUmake)
+] )