boot/uboot: fix uboot building host tools on x86 architecture

The make all command run the tools/makefile on the process.
This makefile use "pkg-config" command to support static link.
The issue is the use of pkg-config configured for crosscompiling
to build binaries tools for host architecture.
To fix it, I add pkg-config environment variable to configure it for host.

Add a test to avoid future regress on the build of U-boot.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
[yann.morin.1998@free.fr:
  - fix mixed space-TAB indentation
  - fix check-package
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>