support/testing: provide entropy to lua tests

support/testing: provide entropy to lua tests

Newer versions of lua-http require entropy.
Switch to use armv5 builtin kernel that already provides entropy for all
lua tests.

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/269139374
https://gitlab.com/buildroot.org/buildroot/-/jobs/269139376

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Francois Perrad <francois.perrad@gadz.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>