Terminate libFuzzer on second SIGINT
Terminate libFuzzer on second SIGINT

Makes it possible to stop the fuzzer even if the fuzz target is in an
infinite loop. The first SIGINT lets the fuzzer exit gracefully if
possible, the second now triggers a hard exit.

CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer