Specifying build directory in AT_CHECK

[Denver Gingerich]

When I run "make check" on GNU wdiff, I would like Autotest to use the
wdiff binary compiled with "make" to run the tests rather than the
wdiff binary in $PATH.  Currently, my AT_CHECK lines look like this:

AT_CHECK([wdiff wdiff-a.txt wdiff-b.txt], ...

Naturally, the above line picks the wdiff binary in the path for
testing, which is not desired.  It seems unreasonable to expect a user
to "make install" to put the binary in their path before running "make
check".  So I would like to change it to something like:

AT_CHECK([$builddir/wdiff wdiff-a.txt wdiff-b.txt], ...

However, I don't know what the appropriate variable to use in place of
$builddir would be.  Is there such a variable?  Is Autotest designed
such that it can do what I'm trying to do with it?

Denver