efibootmgr: new package

efibootmgr: new package

A Linux user-space application to modify the Intel Extensible Firmware
Interface (EFI) Boot Manager. This application can create and destroy
boot entries, change the boot order, change the next running boot
option, and more.

The only issue found was that it was trying to include headers from the
host, so $(STAGING_DIR) has been prepended to the include path so that
the package finds the right headers.

efibootmgr depends on the libraries provided by efivar.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
[Thomas:
  - change the "depends on" for efivar to a "select", and propagate the
    relevant dependencies.
  - the license is GPLv2+, not GPLv2.
  - move the Makefile tweak to a post-patch hook rather than doing it as
    part of the build step.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>