EXEEXT and EXTRA_PROGRAMS

[D M]

        Hello.

        I'm not 100% sure if it is the right group to ask but I'll try. 
I'm trying to compile program which is built condinally. So my Makefile.am 
looks like this:
EXTRA_PROGRAMS=foo
address@hidden@
correspoding configure.in:
if (certain condidtions)
        FOO=foo
AC_SUBST(FOO)

However, if a platform that application is compiled for uses exe
extensions, FOO still gets value 'foo' - resulting Makefile is incorrect
and is not able to compile the app.  I read info pages on EXEEXT but
I found no clear explanation of how such case should be handled
properly. 
Thanks.

-- 
DM