[csmith-project/creduce] 4f83e7: Avoid run-time warning when `bindir` does not exis...

[Eric Eide <eeide@cs.utah.edu>]

  Branch: refs/heads/master
  Home:   https://github.com/csmith-project/creduce
  Commit: 4f83e7aa36656e31b152da7420aa2eae307ea9a5
      https://github.com/csmith-project/creduce/commit/4f83e7aa36656e31b152da7420aa2eae307ea9a5
  Author: Eric Eide <eeide@cs.utah.edu>
  Date:   2016-12-16 (Fri, 16 Dec 2016)

  Changed paths:
    M creduce/pass_clang.pm
    M creduce/pass_clang_binsrch.pm
    M creduce/pass_clex.pm
    M creduce/pass_lines.pm
    M creduce/pass_unifdef.pm

  Log Message:
  -----------
  Avoid run-time warning when `bindir` does not exist.

`abs_path()` returns undef when its argument names a file that does not exist.