ot-br-posix: Add writeable path for data file of the border router

OTBR stores at least one .data file in this path and some functionality
does not work without it being read-write. Mark the path as writable.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>

meta-oniro-staging/recipes-connectivity/openthread/ot-br-posix_git.bb

@@ -28,7 +28,10 @@ S = "${WORKDIR}/git"
 
 DEPENDS = "autoconf-archive dbus readline avahi jsoncpp boost"
 
-inherit cmake systemd
+inherit cmake systemd writables
+
+WRITABLES = "data"
+WRITABLE_PATH[data] = "/var/lib/thread/"
 
 SYSTEMD_SERVICE_${PN} = "otbr-agent.service otbr-web.service"