@file{xm-@var{machine}.h} header, if any, appropriate to the host,
build and target machines respectively, the configuration headers for
the target, and some definitions; for the host and build machines,
@file{xm-@var{machine}.h} header, if any, appropriate to the host,
build and target machines respectively, the configuration headers for
the target, and some definitions; for the host and build machines,