Verify that dwarfdump doesn't crash on invalid line table prologue.
OSS-Fuzz Issue 4644 (https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=4644)

RUN: llvm-dwarfdump --verbose %p/Inputs/invalid.linetable 2>&1 | FileCheck %s --check-prefix=INVALID-LINE-TABLE
INVALID-LINE-TABLE: invalid directory or file table description