Passing default configure parameters in subpackage

Hi!

I placed a copy of each autoconfiscated third-party dependency of my
software as a subdirectory. I then followed the instructions for
building subpackages in autotools (http://www.gnu.org/software/
automake/manual/html_node/Subpackages.html#Subpackages). However,
there is a subpackage that needs to have certain parameters passed to
its configure script. The macro AC_CONFIG_SUBDIRS passes the command
line parameters to the configure script of each subpackage but I do
not want the user to worry about the exact parameters to pass to
configure.

My question now is how do I set the parameters to pass to configure in
my subpackages?