support/scripts/br2-external: add kernel extensions

Buildroot documentation section 9.2.1.6 "Additional kernel extensions"
indicates support for kernel extensions defined in external buildroot
trees but unfortunately, there didn't seem to be any support in
br2-external script.

This patch copies 'init' code support to include external kernel
extensions defined in 'linux' dir at the br2-external root directory as
explained in documentation.

Signed-off-by: Nicolas POIROT <ni.poirot@laposte.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

linux/Config.ext.in

@@ -148,4 +148,7 @@ config BR2_LINUX_KERNEL_EXT_AUFS_VERSION
 
 endif # aufs
 
+# kernel extensions from br2-external trees, if any
+source "$BR2_BASE_DIR/.br2-external.in.linux"
+
 endmenu

support/scripts/br2-external

@@ -163,6 +163,7 @@ do_kconfig() {
         openssl
         skeleton
         init
+        linux
     )
 
     for br2 in "${items[@]}"; do
@@ -242,6 +243,14 @@ do_kconfig() {
         else
             printf '# No init from: %s\n\n' "${br2_desc}"
         fi >>"${outputdir}/.br2-external.in.init"
+
+        if [ -f "${br2_ext}/linux/Config.ext.in" ]; then
+            printf 'comment "linux extension from: %s"\n' "${br2_desc}"
+            printf 'source "%s/linux/Config.ext.in"\n' "${br2_ext}"
+            printf '\n'
+        else
+            printf '# No linux extension from: %s\n\n' "${br2_desc}"
+        fi >>"${outputdir}/.br2-external.in.linux"
     done
 
     printf 'endmenu\n' >>"${outputdir}/.br2-external.in.menus"