Ticket 16673

We found this problem from our ATP Slurm plugin, which uses `spank_get_item` to find the name of the job binary that is being launched. When the `--bcast=<dir>` option is used to ship the job binary to a directory, this causes the first entry in the `argv` array to be the setting of `--bcast` instead of the name or path of the binary. Below is a small reproducer.

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

#include <slurm/spank.h>

#define MAJOR_VER 1
#define MINOR_VER 0
#define FULL_VERSION ((MAJOR_VER * 1000) + MINOR_VER)
SPANK_PLUGIN(launch/test, FULL_VERSION)

int slurm_spank_local_user_init(spank_t sHandle, int argc, char **argv)
{
        int job_argc = 0;
        char const** job_argv = NULL;
        int spank_rc = spank_get_item(sHandle, S_JOB_ARGV, &job_argc, &job_argv);
        if (spank_rc != ESPANK_SUCCESS) {
                slurm_info("%s\n", spank_strerror(spank_rc));
        } else {
                fprintf(stderr, "Job argv: ");
                for (int i = 0; i < job_argc; i++) {
                        fprintf(stderr, "%s ", job_argv[i]);
                }
                fprintf(stderr, "\n");
        }

        return 0;
}

int slurm_spank_exit(spank_t sHandle, int argc, char **argv)
{
        return 0;
}

$ cc -g -O0 -shared `pkg-config --libs --cflags slurm` test_argv.c -o test_argv.so

# Plugstack line
optional /home/users/adangelo/test_argv.so

$ srun -n2 --bcast=/home/users/adangelo/ ./a.out argv1 argv2
Job argv: /home/users/adangelo/ argv1 argv2