the ar tool is called gar on some systems

Some systems that have only installed the GNU toolchain (prefixed with "g")
do not provide "ar" but only "gar".  Make configure find this tool as well.

Signed-off-by: Robert Schiele <rschiele@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

configure.ac

@@ -104,7 +104,7 @@ AC_MSG_NOTICE([CHECKS for programs])
 #
 AC_PROG_CC([cc gcc])
 #AC_PROG_INSTALL		# needs install-sh or install.sh in sources
-AC_CHECK_TOOL(AR, ar, :)
+AC_CHECK_TOOLS(AR, [gar ar], :)
 AC_CHECK_PROGS(TAR, [gtar tar])
 # TCLTK_PATH will be set to some value if we want Tcl/Tk
 # or will be empty otherwise.