wayland-egl: Pass nm path to check script

A previous patch used $NM as an environment variable, but this was only
set as a make variable. Make sure it is passed through from make to the
environment we use to run tests.

v2: Quote argument when passing to shell.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reported-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Fixes: 6903e4d5 ("wayland-egl: use correct `nm` path when cross-compiling")
Cc: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>