meson.bblcass: Remove empty egg-info directories before running meson

sstate.bbclass no longer removes empty directories to avoid a race (see
commit 4f94d929 "sstate/staging: Handle directory creation race issue").
Unfortunately Python apparently treats an empty egg-info directory as if
the version it previously contained still exists and fails if a newer
version is required, which Meson does. To avoid this, make sure there
are no empty egg-info directories from previous versions left behind.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>