[PATCH] kernel: Use hardlinks for do_populate_sysroot for speed

[Richard Purdie <richard.purdie@linuxfoundation.org>]

The kernel tree is large and doesn't need to be copied. Override
the default sysroot handling function to use a hardlink copying
function in python.

This commit also drops the copying of the /lib directory which
just contains the kernel modules. We never use those in the sysroot
so there is little point in carrying those around.

For linux-yocto this takes the do_populate_sysroot time 24s -> 14s.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
index 0b6360f..e793ccb 100644
--- a/meta/classes/kernel.bbclass
+++ b/meta/classes/kernel.bbclass
@@ -308,8 +308,8 @@ kernelscripts_sstate_postinst () {
 	fi
 }
 
-sysroot_stage_all_append() {
-	sysroot_stage_dir ${D}${KERNEL_SRC_PATH} ${SYSROOT_DESTDIR}${KERNEL_SRC_PATH}
+python sysroot_stage_all () {
+    oe.path.copyhardlinktree(d.expand("${D}${KERNEL_SRC_PATH}"), d.expand("${SYSROOT_DESTDIR}${KERNEL_SRC_PATH}"))
 }
 
 kernel_do_configure() {