Tests failing on NixOS due to bad bash path

[christomel]

When running make check after ./bootstrap and ./configure many tests fail to run on NixOS.

Example failure log excerpt:

FAIL: check-globals.sh
======================

../../test-driver: ./check-globals.sh: /bin/bash: bad interpreter: No such file or directory
FAIL check-globals.sh (exit status: 126)

This issue is caused by the scripts wrongly assuming that bash is at /bin/bash. This is not the case for all unix operating systems. The solution for that is to use /usr/bin/env bash instead of hardcoding the path, because the former finds the bash executable in user's PATH, wherever it may be.

Steps to reproduce on NixOS with flakes enabled:

1. git clone https://github.com/OpenDataPlane/odp.git && cd odp
2. nix flake init
3. replace contents of ./flake.nix with the following

{
  description = "A very basic flake";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
  };

  outputs =
    { self, nixpkgs }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
      };
    in
    {
      devShells.${system} = {
        default = pkgs.mkShell {
          packages = with pkgs; [
            libtool
            automake
            autoconf
            asciidoctor
            mscgen
            cunit
            graphviz
            valgrind
            libcli
            pkg-config
            libconfig
            libpcap
            openssl
            doxygen
            onnxruntime
            binutils
            gcc
          ];

          NIX_ENFORCE_NO_NATIVE = 0;
        };
      };

    };
}

4. Enter nix shell using nix develop, then

./bootstrap
./configure
make check

5. You will get the said error