kernel.bbclass: do_sizecheck: update path to build image and do not delete

do_sizecheck has a few issues especially with vmlinux image type.

It breaks because KERNEL_OUTPUT is a path relative to ${B}.  When
do_sizecheck runs it does not find the file (because the working
directory is elsewhere) and does not fail.

Also, the image file referenced by KERNEL_OUTPUT may be a link.

Finally, when do_sizecheck deletes the oversized kernel image it leaves
the previously run do_compile task with inaccurate status.

So, do the following:
 - specify that the working directory should be ${B}
 - use ls -L to reference to the real file, and ensure that the link
   file is created
 - keep the oversized image file so the status of do_compile is valid

[YOCTO #3514]

(From OE-Core rev: f0b19ddce3c92c5d06976cf73d4c4c480e053dff)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Michel Thebeau <michel.thebeau@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel.bbclass

@@ -293,15 +293,16 @@ python split_kernel_packages () {
 # with a fixed length or there is a limit in transferring the kernel to memory
 do_sizecheck() {
 	if [ ! -z "${KERNEL_IMAGE_MAXSIZE}" ]; then
-		size=`ls -l ${KERNEL_OUTPUT} | awk '{ print $5}'`
+		cd ${B}
+		size=`ls -lL ${KERNEL_OUTPUT} | awk '{ print $5}'`
 		if [ $size -ge ${KERNEL_IMAGE_MAXSIZE} ]; then
-			rm ${KERNEL_OUTPUT}
 			die "This kernel (size=$size > ${KERNEL_IMAGE_MAXSIZE}) is too big for your device. Please reduce the size of the kernel by making more of it modular."
 		fi
 	fi
 }
+do_sizecheck[dirs] = "${B}"
 
-addtask sizecheck before do_install after do_compile
+addtask sizecheck before do_install after do_kernel_link_vmlinux
 
 KERNEL_IMAGE_BASE_NAME ?= "${KERNEL_IMAGETYPE}-${PE}-${PV}-${PR}-${MACHINE}-${DATETIME}"
 # Don't include the DATETIME variable in the sstate package signatures