meta-quanta: layer.conf: set BBFILE_PATTERN

Bitbake uses this regex to associate recipes and bbappends from BBFILES
(which contains recipes and bbappends from -all- layers listed in
bblayers.conf) to this layer.  The association is then used to map the
BBFILE_PRIORITY value for this layer onto the recipes provided by this
layer.

BBFILE_PRIORITY is used to determine which recipe to use when the same
recipe appears in multiple layers.

Without BBFILE_PATTERN set, recipes in this layer will get a default
priority and not the priority specified in BBFILE_PRIORITY.

This layer doesn't set a priority anyway, so functionally this patch is
a noop but it is an improvement from a correctness standpoint, and it
makes a warning go away

Removes warning:
WARNING: No bb files matched BBFILE_PATTERN_quanta ''

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I40ed61184e6a1705e8dead097b6afd9a3a69c2b9
diff --git a/conf/layer.conf b/conf/layer.conf
index 8bbd31d..fb4c083 100644
--- a/conf/layer.conf
+++ b/conf/layer.conf
@@ -2,7 +2,7 @@
 BBPATH .= ":${LAYERDIR}"
 
 BBFILE_COLLECTIONS += "quanta"
-BBFILE_PATTERN_quanta = ""
+BBFILE_PATTERN_quanta := "^${LAYERDIR}/"
 
 # Provide a variable that points the base of the quanta layer.
 QUANTABASE = '${@os.path.normpath("${LAYERDIR}/")}'