CI: Get Travis CI vestige sorted in build.sh.

CI: Get Travis CI vestige sorted in build.sh.

Compiling user-provided source code and running the resulting binary
with sudo was a security problem, thus instead of fixing two no-op
blocks remove them altogether. If anyone later needs to debug features
that require higher privileges, they will need to come up with a better
solution. Simplify the debug output test condition and rephrase the
associated comment for clarity.