builddeb: generate multi-arch friendly linux-libc-dev package

Debian-based distributions place libc header files in a machine
specific directory (/usr/include/<libc-machine>) instead of
/usr/include/asm to support installation of the linux-libc-dev
package from multiple architectures. Move headers installed by
"make headers_install" accordingly using Debian's tuple from
dpkg-architecture (stored in debian/arch).

Signed-off-by: Cedric Hombourger <Cedric_Hombourger@mentor.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/package/mkdebian

@@ -197,6 +197,7 @@ Architecture: $debarch
 Description: Linux support headers for userspace development
  This package provides userspaces headers from the Linux kernel.  These headers
  are used by the installed headers for GNU glibc and other system libraries.
+Multi-Arch: same
 
 Package: $dbg_packagename
 Section: debug