kernel: copy defconfig to {B} vs {S}

For kernel's that use a split source/object build the copy
of defconfig to {S} in the base kernel class is problematic.
The previous solution for this was to override the do_configure
of the base kernel class in a subclass. While this is still
a viable/valid option, it does mean that changes to the base
do_configure will be missed.

The solution to this is to copy a defconfig to {B} which is
typically the same as {S}, so most kernel recipes won't see or
care about this change.

With this change in place, linux-yocto.bbclass can drop its
override of do_configure.

Tested with linux-yocto and oe linux recipes.

(From OE-Core rev: 4f03d922ce32f602a5a407cf422d82a0d036e4a0)

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

meta/classes/kernel-yocto.bbclass

@@ -118,12 +118,6 @@ python do_kernel_configcheck() {
     bb.plain( "%s" % result )
 }
 
-# overrides the base kernel_do_configure, since we don't want all the
-# defconfig processing in there
-kernel_do_configure() {
-        yes '' | oe_runmake oldconfig
-}
-
 
 # Ensure that the branches (BSP and meta) are on the locatios specified by
 # their SRCREV values. If they are NOT on the right commits, the branches

meta/classes/kernel.bbclass

@@ -181,8 +181,8 @@ sysroot_stage_all_append() {
 kernel_do_configure() {
 	# Copy defconfig to .config if .config does not exist. This allows
 	# recipes to manage the .config themselves in do_configure_prepend().
-	if [ -f "${WORKDIR}/defconfig" ] && [ ! -f "${S}/.config" ]; then
-		cp "${WORKDIR}/defconfig" "${S}/.config"
+	if [ -f "${WORKDIR}/defconfig" ] && [ ! -f "${B}/.config" ]; then
+		cp "${WORKDIR}/defconfig" "${B}/.config"
 	fi
 	yes '' | oe_runmake oldconfig