configure with datadir outside of --prefix fails with meson

[Anthony PERARD]

Hi,

When we build QEMU while building Xen we do:
    ./configure --prefix=/usr/lib/xen \
                --datadir=/usr/share/qemu-xen \
                ...

But meson give an error:
  ERROR: The value of the 'datadir' option is '/usr/share/qemu-xen' which must 
be a subdir of the prefix '/usr/lib/xen'.

Would it still be possible to allow datadir outside of prefix or is it
going to be a limitation imposed by meson?

I can always change the call to configure but it would be nice not to
have to.

Thanks,

-- 
Anthony PERARD