When looking for the next directory component, a "." component is now skipped.

This fixes the path(s) used for firmware lookup for the prefix == bindir case
which is standard for QEMU on Windows and where the internally
used bindir value ends with "/.".

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Message-Id: <20210208205752.2488774-1-sw@weilnetz.de>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>