meta-evb: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I7a755976c2144356314faef7cf1f226ae18dc884
diff --git a/meta-evb/meta-evb-raspberrypi/conf/local.conf.sample b/meta-evb/meta-evb-raspberrypi/conf/local.conf.sample
index a33ae30..fa7e006 100644
--- a/meta-evb/meta-evb-raspberrypi/conf/local.conf.sample
+++ b/meta-evb/meta-evb-raspberrypi/conf/local.conf.sample
@@ -1,11 +1,11 @@
 MACHINE ??= "raspberrypi"
 DISTRO ?= "openbmc-phosphor"
 PACKAGE_CLASSES ?= "package_rpm"
-SANITY_TESTED_DISTROS_append ?= " *"
-EXTRA_IMAGE_FEATURES = "debug-tweaks"
-USER_CLASSES ?= "buildstats image-prelink"
+SANITY_TESTED_DISTROS:append ?= " *"
+EXTRA_IMAGE_FEATURES ?= "debug-tweaks"
+USER_CLASSES ?= "buildstats"
 PATCHRESOLVE = "noop"
-BB_DISKMON_DIRS = "\
+BB_DISKMON_DIRS ??= "\
     STOPTASKS,${TMPDIR},1G,100K \
     STOPTASKS,${DL_DIR},1G,100K \
     STOPTASKS,${SSTATE_DIR},1G,100K \