Enable subdir-objects for automake

Follow the advice automake gives us:

    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: Roland Dreier <roland@purestorage.com>
1 file changed