kernel-yocto: fix diffconfig/kernel_configme breakage

The bbclass did the following:

    do_diffconfig[depends] += "virtual/kernel:do_kernel_configme"

This clearly introduces a cross-kernel task dependency if the recipe
inheriting this class isn't the preferred provider of virtual/kernel, which is
obviously wrong, but further, will break the build if a kernel-yocto based
kernel is parsed and not skipped, but virtual/kernel refers to
a non-kernel-yocto recipe, which would not have the do_kernel_configme task.

Work around this by adding the in-recipe task dep programmatically with
bb.build.addtask when do_diffconfig exists.

(From OE-Core rev: 0e6881146d87f0d214d80bc92e54c113906db63a)

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel-yocto.bbclass

@@ -263,6 +263,8 @@ do_kernel_configme() {
 	echo "CONFIG_LOCALVERSION="\"${LINUX_VERSION_EXTENSION}\" >> ${B}/.config
 }
 
+addtask kernel_configme after do_patch
+
 python do_kernel_configcheck() {
     import re, string, sys
 
@@ -407,4 +409,8 @@ OE_TERMINAL_EXPORTS += "GUILT_BASE KBUILD_OUTPUT"
 GUILT_BASE = "meta"
 KBUILD_OUTPUT = "${B}"
 
-do_diffconfig[depends] += "virtual/kernel:do_kernel_configme"
+python () {
+    # If diffconfig is available, ensure it runs after kernel_configme
+    if 'do_diffconfig' in d:
+        bb.build.addtask('do_diffconfig', None, 'do_kernel_configme', d)
+}