tools-hardened/desktop: Adds kernel source population in chroot

In order to make the building of the ISO non-reliant on any sort of
external settings from the build system, the kernel source for needs
to be populated into the chroot, along with the pre-made kernel config.

tools-hardened/desktop/gnome3-run.sh

@@ -71,6 +71,7 @@ setup_confs() {
 main() {
 	unpack_stage3
 	mount_dirs
+    populate_kernel_src
 	populate_etc
 	rebuild_toolchain
 	rebuild_world