Linking in an externally compiled .o file with gnatmake?

[Jacob Sparre Andersen <sparre@nbi.dk>]

I'm working on a binding to the Linux sound API ALSA
(http://repositories.jacob-sparre.dk/alsa-binding).  As a part of the
binding, I need to access a C macro.  I do that by turning the macro
into a C function:

% cat alsa_macros.c
#include <alsa/asoundlib.h>

void allocate_alsa_hardware_parameters (snd_pcm_hw_params_t **hwparams_ptr) {
   snd_pcm_hw_params_alloca (hwparams_ptr);
};
%

Compiling "alsa_macros.c" to "alsa_macros.o" is not a problem, but how
can I get gnatmake to link "alsa_macros.o" into the final program?  Or
maybe into "sound-alsa.o" as it is package Sound.ALSA which imports the
function.

Greetings,

Jacob
-- 
"Facts are stubborn, but statistics are more pliable." -- Mark Twain