kbuild: kallsyms allow 3-pass generation if symbols size has changed

	#     the right size, but due to the added section, some

	#     addresses have shifted.

	#     From here, we generate a correct .tmp_kallsyms2.o

	# 2a) We may use an extra pass as this has been necessary to

	#     woraround some alignment related bugs.

	#     KALLSYMS_EXTRA_PASS=1 is used to trigger this.

	# 3)  The correct ${kallsymso} is linked into the final vmlinux.

	# 3)  That link may have expanded the kernel image enough that

	#     more linker branch stubs / trampolines had to be added, which

	#     introduces new names, which further expands kallsyms. Do another

	#     pass if that is the case. In theory it's possible this results

	#     in even more stubs, but unlikely.

	#     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around

	#     other bugs.

	# 4)  The correct ${kallsymso} is linked into the final vmlinux.

	#

	# a)  Verify that the System.map from vmlinux matches the map from

	#     ${kallsymso}.

	vmlinux_link .tmp_kallsyms1.o .tmp_vmlinux2

	kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o

	# step 2a

	if [ -n "${KALLSYMS_EXTRA_PASS}" ]; then

	# step 3

	size1=$(stat -c "%s" .tmp_kallsyms1.o)

	size2=$(stat -c "%s" .tmp_kallsyms2.o)

	if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then

		kallsymso=.tmp_kallsyms3.o

		kallsyms_vmlinux=.tmp_vmlinux3