Please note (again) that you don't have to compile your own version: if
you are using a Linux system based on ELF executables, you can use the
binary in bin-linux/xwatch. But if you really want to compile all,
follow these steps.
xwatch. Check the Makefile in the src subdirectory for
two ftp sites that carry XForms for Linux. Obtain the library and
install it. (Even if you don't want to compile XWatch, you'll need the
shared libraries. They may or may not already be installed on your
system.) XWatch will happily run with XForms version 0.81.
src subdirectory, edit the Makefile and adjust
some defines at the top. E.g., a make install copies the binary by
default to /usr/local/X11/bin; adjust that if you don't like this
behavior.
make install, followed by a make clean.
XWatch.ap from the source directory to
/usr/lib/X11/app-defaults/XWatch. Edit the file and state your
favorite settings.
xwatch with some file arguments in
your logfiles directory. If you're satisfied with the appearance and
workings of xwatch, add the invocation to your script that starts
an X session.