Debian:kernel-signed: Added signed packages into debian_pkg_dirs_sign

Added the kernel signed packages into 'debian_pkg_dirs_sign',
then these packages can be discovered and built by build-pkgs.
This causes the new build type 'sign' created and it has the
lowest priority which make sure that the signed packages should
be built in the last batch in 'distro' layer.
The reason for adding build type 'sign' is also described in the
related commit [Add build type sign and set the priority in distro]
in starlingx/tools,
from https://review.opendev.org/c/starlingx/tools/+/842663

Test Plan:
Pass: build-pkgs -a
Pass: build-pkgs -a -l <layer>
Pass: Make sure linux and linux-rt has been built
      Run the script to sign the kernel
      build-pkgs -b sign -p kernel-std-signed, kernel-rt-signed

Depends-On: https://review.opendev.org/c/starlingx/tools/+/842663

Story: 2009221
Task: 45383

Signed-off-by: Haiqing Bai <haiqing.bai@windriver.com>
Change-Id: I4de8c632e2e17d1111e4bce1e246d924be65c373

debian_pkg_dirs_sign

@@ -0,0 +1,2 @@
+kernel-signed/kernel-rt-signed
+kernel-signed/kernel-std-signed

kernel-signed/kernel-rt-signed/debian/dl_hook

@@ -26,7 +26,7 @@
 mkdir "$1"
 cd "$1" || exit 1
 
-file_debian=(../../linux-rt/linux-signed-*.tar.xz)
+file_debian=(../../../rt/linux-rt/linux-signed-*.tar.xz)
 if [ ! -f "${file_debian}" ]
 then
     echo "Please create signatures first (e.g. use debian-test-sign)!"

kernel-signed/kernel-std-signed/debian/dl_hook

@@ -26,7 +26,7 @@
 mkdir "$1"
 cd "$1" || exit 1
 
-file_debian=(../../linux/linux-signed-*.tar.xz)
+file_debian=(../../../std/linux/linux-signed-*.tar.xz)
 if [ ! -f "${file_debian}" ]
 then
     echo "Please create signatures first (e.g. use debian-test-sign)!"