Fix: Dump executable base-address with readlink

The previous approach only worked if the traced executable was invoked
via its fully qualified path. Using readlink to determine the full
qualified path of the traced executable works reliably even when the
traced executable is started via PATH lookup.

Signed-off-by: Paul Woegerer <paul_woegerer@mentor.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>