cereal: Favor ALLOW_EMPTY

A number of recipes remove PN from the package list.  While this
seems to work it is unconventional and puts us into dusty corners
of oe-core/bitbake.

Adopt a more conventional approach with ALLOW_EMPTY_${PN} = "1".

Change-Id: I62a980f1b826f79bdba1bd4179b6f491665fe33c
Tested: Built cereal and validated package contents
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/common/recipes-support/serialization/cereal_1.2.2.bb b/common/recipes-support/serialization/cereal_1.2.2.bb
index 8dd1d69..9b60187 100644
--- a/common/recipes-support/serialization/cereal_1.2.2.bb
+++ b/common/recipes-support/serialization/cereal_1.2.2.bb
@@ -11,9 +11,7 @@
 
 S = "${WORKDIR}/git"
 
-PACKAGES_remove = "${PN}*"
-PACKAGES = "${PN}-dev"
-RDEPENDS_${PN}-dev = ""
+ALLOW_EMPTY_${PN} = "1"
 
 do_install () {
     install -d ${D}${includedir}/cereal