Add meta-clang to bblayers.conf

Allow using the clang 12 based toolchain

Signed-off-by: Bernhard Rosenkränzer <bernhard.rosenkraenzer.ext@huawei.com>

flavours/linux/bblayers.conf.sample

@@ -12,6 +12,7 @@ BBFILES ?= ""
 BBLAYERS ?= " \
   ##OEROOT##/meta \
   ##OEROOT##/meta-poky \
+  ##OEROOT##/meta-clang \
   ##OEROOT##/meta-yocto-bsp \
   ##OEROOT##/../meta-freertos \
   ##OEROOT##/../meta-zephyr \