autoconf help

[Glen Cornell]

I'm trying to incorporate the xfree86 loader into the rtems tree at the
location:

c/src/libmisc/loader

I've managed to create a Makefile.ac that uses conditionals to support the
target object file formats such as in the example below:

if elf_loader
# Using the elf loader:
ELF_SRCS = elfloader.c
ELF_FLAGS = -DELF_SUPPORT
endif

My question is that how do I set up the conditional in my configure.in script? 
How do I know what object file formats are supported by the cross compiler?  I
thought that this might be a starting point:

AM_CONDITIONAL(elf_loader, i386-rtems-objdump --info | grep elf)

Is there an easier/better way?

One last question, how do I specify the proper cross objdump to use?

TIA,
glenco