populate_sdk: Handle OLDEST_KERNEL

Add a check to the SDK so that it only runs on systems with kernel versions
it supports.

[YOCTO #6856]

(From OE-Core rev: b4caa8085aa15674162ff5135b13409998db9510)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/populate_sdk_base.bbclass

@@ -126,6 +126,7 @@ EOF
 	# substitute variables
 	sed -i -e 's#@SDK_ARCH@#${SDK_ARCH}#g' \
 		-e 's#@SDKPATH@#${SDKPATH}#g' \
+		-e 's#@OLDEST_KERNEL@#${OLDEST_KERNEL}#g' \
 		-e 's#@REAL_MULTIMACH_TARGET_SYS@#${REAL_MULTIMACH_TARGET_SYS}#g' \
 		-e '/@SDK_POST_INSTALL_COMMAND@/d' \
 		${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.sh