xc-am-iface.m4: provide XC_AUTOMAKE macro

m4/xc-am-iface.m4

+#---------------------------------------------------------------------------
+#
+# xc-am-iface.m4
+#
+# Copyright (c) 2013 Daniel Stenberg <daniel@haxx.se>
+#
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+#
+#---------------------------------------------------------------------------
+
+# serial 1
+
+
+dnl _XC_AUTOMAKE_BODY
+dnl -------------------------------------------------
+dnl Private macro.
+dnl
+dnl This macro performs embedding of automake initialization
+dnl code into configure script. When automake version 1.14 or
+dnl newer is used at configure script generation time, this
+dnl results in 'subdir-objects' automake option being used.
+dnl When using automake versions older than 1.14 this option
+dnl is not used when generating configure script.
+
+m4_define([_XC_AUTOMAKE_BODY],
+[dnl
+## --------------------------------------- ##
+##  Start of automake initialization code  ##
+## --------------------------------------- ##
+m4_ifdef([_AM_PROG_CC_C_O],
+[
+AM_INIT_AUTOMAKE([subdir-objects])
+],[
+AM_INIT_AUTOMAKE
+])dnl
+## ------------------------------------- ##
+##  End of automake initialization code  ##
+## ------------------------------------- ##
+dnl
+m4_define([$0], [])[]dnl
+])
+
+
+dnl XC_AUTOMAKE
+dnl -------------------------------------------------
+dnl Public macro.
+dnl
+dnl This macro embeds automake machinery into configure
+dnl script with initialization option 'subdir-objects'
+dnl when using automake version 1.14 or newer.
+
+AC_DEFUN([XC_AUTOMAKE],
+[dnl
+AC_PREREQ([2.50])dnl
+dnl
+AC_BEFORE([$0],[AM_INIT_AUTOMAKE])dnl
+dnl
+_XC_AUTOMAKE_BODY
+dnl
+m4_ifdef([AM_INIT_AUTOMAKE],
+  [m4_undefine([AM_INIT_AUTOMAKE])])dnl
+dnl
+m4_define([$0], [])[]dnl
+])
+