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>

 # libelf config file

 choice

     bool

     prompt "libelf version"

 # Don't remove next line

 # CT_INSERT_VERSION_BELOW

 config LIBELF_V_0_8_13

     bool

     prompt "0.8.13"

 config LIBELF_V_0_8_12

     bool

     prompt "0.8.12"

 endchoice

 config LIBELF_VERSION

     string

 # Don't remove next line

 # CT_INSERT_VERSION_STRING_BELOW

     default "0.8.13" if LIBELF_V_0_8_13

     default "0.8.12" if LIBELF_V_0_8_12