Tests that require PRNG are by default seeded from `/dev/urandom`.
However, the user should be able to override with a given seed
to reproduce a failing test.
Instead of messing with command-line arguments, a cleaner approach
is to fetch the seed from an environment variable.
Do not force 64-bit `time_t` on 32-bit platforms, since libfuse
does not do so. Linking shared objects with incompatible types
breaks ABI, resulting in undefined behavior.
Instead, add run-time checks to make sure that timestamps do not
overflow. If they do, set to `INT32_MAX`.
Also tidy up build scripts, tests, and the installation guide.
- If the utility library is not built, link to the existing library
when building helper programs for filesystem tests.
- Refactor PRNG seeding in tests.