dbind/Makefile.am: specify subdir-objects automake option
As recommended during autoreconf:
dbind/Makefile.am:1: while processing Libtool library 'libdbind.la'
dbind/Makefile.am:23: warning: source file '../atspi/atspi-gmain.c' is in a subdirectory,
dbind/Makefile.am:23: but option 'subdir-objects' is disabled
automake: warning: possible forward-incompatibility.
automake: At least a source file is in a subdirectory, but the 'subdir-objects'
automake: automake option hasn't been enabled. For now, the corresponding output
automake: object file(s) will be placed in the top-level directory. However,
automake: this behaviour will change in future Automake versions: they will
automake: unconditionally cause object files to be placed in the same subdirectory
automake: of the corresponding sources.
automake: You are advised to start using 'subdir-objects' option throughout your
automake: project, to avoid future incompatibilities.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>