Do the DO-178 standards include guidelines on cyclomatic complexity?
Short answer is No.

From the note after 5.2.2.g


  The current state of software engineering does not permit a quantitative
  correlation between complexity and the attainment of system safety objectives.
  While no objective guidance can be provided, the software design process should
  avoid introducing complexity because as the complexity of software increases, it
  becomes more difficult to verify the design and to show that the safety-related
  requirements are satisfied.


DO-178C is focused on defining process objectives rather than design guidelines.  Your process (specifically Design Standards) might specify a certain maximum complexity value, but it wouldn't be driven directly from DO-178C