UBUNTU: [Packaging] Replace Perl oneliner with Bash statements

UBUNTU: [Packaging] Replace Perl oneliner with Bash statements

Replace the only Perl oneliner in the Ubuntu Makefiles with Bash
statements. This brings us one step closer to dropping Perl as a build
dependency for the Ubuntu kernel.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>