configure.ac: Use autoconf macro for GNU make.

configure.ac

@@ -53,7 +53,7 @@ AC_PROG_CC
 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

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)
+] )