[gparted] Implement libtoolize suggestion setting ACLOCAL_AMFLAGS

[Curtis Gedak <gedakc src gnome org>]

commit 9af41093f8856deea75c572e3195744334e85abb
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue Apr 11 16:03:40 2017 +0100

    Implement libtoolize suggestion setting ACLOCAL_AMFLAGS
    
    Running ./autogen.sh reports this suggestion:
        libtoolize: Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
    
    Add suggested setting as it causes no difference and silences the
    suggestion.
    
    The Libtool Manual, 5.5.1 Invoking libtoolize
    https://www.gnu.org/software/libtool/manual/html_node/Invoking-libtoolize.html
    
        "If libtoolize detects an explicit call to AC_CONFIG_MACRO_DIRS (see
        The Autoconf Manual in The Autoconf Manual) in your configure.ac, it
        will put the Libtool macros in the specified directory.
    
        In the future other Autotools will automatically check the contents
        of AC_CONFIG_MACRO_DIRS, but at the moment it is more portable to
        add the macro directory to ACLOCAL_AMFLAGS in Makefile.am, which is
        where the tools currently look. If libtoolize doesn't see
        AC_CONFIG_MACRO_DIRS, it too will honour the first '-I' argument in
        ACLOCAL_AMFLAGS when choosing a directory to store libtool
        configuration macros in. It is perfectly sensible to use both
        AC_CONFIG_MACRO_DIRS and ACLOCAL_AMFLAGS, as long as they are kept
        in synchronisation.
    
            ACLOCAL_AMFLAGS = -I m4
        "

 Makefile.am |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 5045877..e88b0d3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,5 @@
+ACLOCAL_AMFLAGS = -I m4
+
 SUBDIRS = compose data doc include lib po src tests
 # Only build GParted help documentation when enabled.  (Can be disabled
 # with './configure --disable-doc').