efivar: 0.7 -> 0.21

Upgrade efivar from 0.7 to 0.21.

* update HOMEPAGE and git repo.
* update license file checksum. It made FSF addresses in COPYING be URLs.
  Ref: https://github.com/rhinstaller/efivar/commit/ca88012


* add -native recipe to provide command makeguids
  and add patch for target package to use this native makeguids command
* add patch to build efivar-native with lower version gcc which doesn't
  support options '-Wmaybe-uninitialized' and '-std=gnu11'

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>