The install script tries to make sure that directories exist before
copying files into them. However, there's at least one spot where it
doesn't check the individual components of the path, causing it to
skip files if you install to a fresh, empty directory.
For example, if you set INSTALL_ROOT to "/tmp/fake-root", the man
pages are not installed because ensure_dirs tries to
without first checking that /tmp/fake-root/share exists.
Changing "mkdir" to "mkdir -p" makes it work again, but I'm not sure
how portable that is.