scripts: add the KDEB_ADDITIONAL_CONTROL knob to builddeb

This lets builders configure the resulting .deb a bit more. Especially, this lets builders choose to add additional dependencies, such as e.g. adding initramfs-tools in Debian-like, which will generate the initramfs for the newly installed package.

---
 scripts/package/builddeb | 1 +
 1 file changed, 1 insertion(+)

index b4f0f2b3f8d2..1e5c42c9481a 100755
@@ -307,6 +307,7 @@ Architecture: any
 Description: Linux kernel, version $version
  This package contains the Linux kernel, modules and corresponding other
  files, version: $version.
+$KDEB_ADDITIONAL_CONTROL
 EOF
 
 fi

2.14.3