The build instruction documentation j2se/src/share/doc/build/build-solaris.html in J2SE 1.4.2 workspace is not quite clear in the "Solaris Build Tools and Libraries Setup" -> "Motif 2.1" section.

In the directory structure it states Xm and lib are from /usr/include/Xm and /usr/dt/lib, but it's more clear to specify that they are from Solaris 7 in the text as well.