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>

 # ISL options

 choice

     bool

     prompt "ISL version"

 # Don't remove next line

 # CT_INSERT_VERSION_BELOW

 config ISL_V_0_12_2

     bool

     prompt "0.12.2"

 config ISL_V_0_11_1

     bool

     prompt "0.11.1"

 endchoice

 config ISL_VERSION

     string

 # Don't remove next line

 # CT_INSERT_VERSION_STRING_BELOW

     default "0.12.2" if ISL_V_0_12_2

     default "0.11.1" if ISL_V_0_11_1