vtr_flow scripts search executable from system paths prior to ${VTR_ROOT} directory

[tangxifan]

I am not sure if this should be considered a bug. Here is my context:
We installed a version of ABC in the system path, i.e., /usr/local/bin/abc, which is different than the version inside the vtr project.
When executing the vtr regression test script ./run_reg_test.pl vtr_reg_strong -show_failures -j20, it reports errors like

Traceback (most recent call last):
  File "/research/ece/lnis/USERS/tang/github/vtr-verilog-to-routing/vtr_flow/scripts/run_vtr_flow.py", line 647, in <module>
    retval = main()
  File "/research/ece/lnis/USERS/tang/github/vtr-verilog-to-routing/vtr_flow/scripts/run_vtr_flow.py", line 376, in main
    return vtr_command_main(sys.argv[1:], prog=sys.argv[0])
  File "/research/ece/lnis/USERS/tang/github/vtr-verilog-to-routing/vtr_flow/scripts/run_vtr_flow.py", line 435, in vtr_command_main
    check_place = args.check_place,
  File "/research/ece/lnis/USERS/tang/github/vtr-verilog-to-routing/vtr_flow/scripts/python_libs/vtr/flow.py", line 205, in run
    use_old_abc_script=use_old_abc_script,
  File "/research/ece/lnis/USERS/tang/github/vtr-verilog-to-routing/vtr_flow/scripts/python_libs/vtr/abc/abc.py", line 101, in run
    shutil.copyfile(str(abc_rc), str(temp_dir / "abc.rc"))
  File "/usr/lib64/python3.6/shutil.py", line 120, in copyfile
    with open(src, 'rb') as fsrc:
FileNotFoundError: [Errno 2] No such file or directory: '/usr/local/bin/abc.rc'

I checked the abc.py script, it seems that the vtr_flow scripts search executable from system paths prior to vtr_root directory.

    abc_exec = find_vtr_file("abc", is_executable=True) if abc_exec is None else abc_exec
    abc_rc = Path(abc_exec).parent / "abc.rc" if abc_rc is None else abc_rc

Expected Behaviour

The regression test script, as well as vtr_flow scripts, are supposed to run without these impacts from system paths.
The vtr_flow script should find executables first from the ${VTR_ROOT} directory rather than the system path.

Current Behaviour

The vtr_flow script spots an ABC executable from system path and most of the regression test failed in a local machine.

Possible Solution

Patch the vtr_flow script, maybe the find_vtr_file() function, to set priority in searching executables.

Steps to Reproduce

1. Install an ABC to the system path, e.g., /usr/local/bin/
2. Git clone the VTR repository
3. Compile and run strong regression tests

    ./run_reg_test.pl vtr_reg_strong -show_failures -j20

Context

Your Environment

• VTR revision used:
  Latest VTR master
• Operating System and version:
  CentOS 7
• Compiler version:
  GCC-8.4

[vaughnbetz]

Adding @sshadtorrie

[jgoeders]

Fixed with #1532