Fix nice level for fuzzer invocation.
The current invocation sets the nice level to 19, or the most nice value
possible. This is incorrect for performance measurements.
Invocation of negative nice values requires the -n flag, in addition to
root permission on most systems.
#!/usr/bin/env bash
set -euo pipefail
cargo rustc --release -- -C target-cpu=native
-nice -20 env RUST_BACKTRACE=1 ./target/release/fuzzer 2>&1 | tee -a output
+sudo nice -n -20 env RUST_BACKTRACE=1 ./target/release/fuzzer 2>&1 | tee -a output
