configure: require automake >= 1.9 for tar-ustar option.

configure: require automake >= 1.9 for tar-ustar option.

By default, newer automake versions make tar use the ancient tar V7 format
that limits filenames to 99 characters. This is troublesome for certain shader
sources files. Now require automake 1.9 and use the tar-ustar option so that
a newer format, defined in POSIX 1003.1-1988, is used. The limitation is now
256 characters.

PAX interchange format (POSIX 1003.1-2001) was considered but probably still
to young? Just stick to the intermediate format for now as this is enough for
our purposes.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>