make sure test are run as a unprivaliged user

Since the whole idea to falsely report additional privalages
make sure the user invoking the test doesn't alread have them.
add void for no arguments
remove a backslash from \ls

bash seems to happily accepts backslashes, e.g. \l\s
works fine. Likely because it are unrecognized escape
sequences. Anyway, remove the backslash as it is likely
a typo.
use cc for the host compiler

FreeBSD e.g. no longer installs gcc by default but uses
clang as host compiler. Hence use cc which should always
work.