kernel: fix out of tree module builds

With the kernel build optimizations, we no longer copy the source from
the built kernel into the staging dir, since the kernel is unpacked and built
directly from the staging dir.

This means that a few build artifacts need to be restored to allow out of
tree modules to once again build.

(From OE-Core rev: 4b981e4fd5a4744d0d83053219274296e7785e77)

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

meta/classes/kernel.bbclass

@@ -223,6 +223,29 @@ kernel_do_install() {
 	#
 
 	echo "${KERNEL_VERSION}" > $kerneldir/kernel-abiversion
+	
+	# Copy files required for module builds
+	cp System.map $kerneldir/System.map-${KERNEL_VERSION}
+	cp Module.symvers $kerneldir/
+	cp .config $kerneldir/
+	mkdir -p $kerneldir/include/config
+	cp include/config/kernel.release $kerneldir/include/config/kernel.release
+
+	# As of Linux kernel version 3.0.1, the clean target removes
+	# arch/powerpc/lib/crtsavres.o which is present in
+	# KBUILD_LDFLAGS_MODULE, making it required to build external modules.
+	if [ ${ARCH} = "powerpc" ]; then
+		mkdir -p $kerneldir/arch/powerpc/lib/
+		cp arch/powerpc/lib/crtsavres.o $kerneldir/arch/powerpc/lib/crtsavres.o
+	fi
+
+	mkdir -p $kerneldir/include/generated/
+	cp -fR include/generated/* $kerneldir/include/generated/
+
+	if [ -d arch/${ARCH}/include/generated ]; then
+		mkdir -p $kerneldir/arch/${ARCH}/include/generated/
+		cp -fR arch/${ARCH}/include/generated/* $kerneldir/arch/${ARCH}/include/generated/
+	fi
 }
 do_install[prefuncs] += "package_get_auto_pr"