Update build instructions in developer documentation

The build now includes the documentation by default.  Add an example of
how to build without it.

Also add an example of how to build without running tests.

According to [1] it is recommended to always build with the `clean`
target.  Add this in the example.

[1] https://groups.google.com/d/msg/repo-discuss/-eNRfFKi74s/ZuImeSLmCJAJ

Change-Id: I909a8c45a59caf6a84e50ca3031566582f3faa93
1 file changed