all: fix wildcard to work with make-4.x

In make-3.8x, the $(wildacrd) function would sort the entries,
while in make-4.x, it would just return the entries in any
unpredictable order [*]

Use the $(sort) function to get reproducible behaviour.

[*] Well, most probably the roder the entries appear when read
from readdir()

Reported-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>

# Bare metal config options

## select BARE_METAL

##

## help 'Bare metal' refers to those programs that run without any kernel.

## help

## help You probably want to say 'y' here if you plan to use your compiler

## help to build bootloaders. It is not yet suitable to build Linux kernels,

## help though, because the APCI stuff relies on the target C library headers

## help being available?!?!...