build: adjust meson dependency for cereal
build: adjust meson dependency for cereal

Cereal does not provide a package-config file for Meson to
use to find it, so we have to look for it at a system level
by checking for the header rather than as a normal dependency
look-up.

Tested by compiling package under bitbake.

Signed-off-by: Patrick Williams <cbb7353e6d953ef360baf960c122346276c6e320@stwcx.xyz>
Change-Id: I28b7f689e352761c5c736fcfac489de193149fc0

openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging