meson.build has one test where "main" is declared unnecessarily
with argc and argv arguments, but does not use them.  Because
the test needs -Werror too, HAVE_BROKEN_SIZE_MAX is defined
incorrectly.

Fix the test and, for consistency, remove argc and argv whenever
they are not needed.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>