Allow run-as-root if 2 envars are set

[rhc54]

Per suggestion by @bangerth, allow mpirun to execute as root if two
envars are set to specific values

Per conversation with @jsquyres, name the envars OMPI_ALLOW_RUN_AS_ROOT
and OMPI_ALLOW_RUN_AS_ROOT_CONFIRM

Fixes #4451

Signed-off-by: Ralph Castain rhc@open-mpi.org

[jsquyres]

@rhc54 I added more text to the man page.

[simonbyrne]

Should this part be changed as well?:

ompi/orte/tools/orterun/orterun.c

Lines 144 to 160 in ae1f7e0

	if (0 == geteuid() && !orte_cmd_options.run_as_root) {
	fprintf(stderr, "--------------------------------------------------------------------------\n");
	if (NULL != orte_cmd_options.help) {
	fprintf(stderr, "%s cannot provide the help message when run as root.\n", orte_basename);
	} else {
	/* show_help is not yet available, so print an error manually */
	fprintf(stderr, "%s has detected an attempt to run as root.\n", orte_basename);
	}
	fprintf(stderr, "Running at root is *strongly* discouraged as any mistake (e.g., in\n");
	fprintf(stderr, "defining TMPDIR) or bug can result in catastrophic damage to the OS\n");
	fprintf(stderr, "file system, leaving your system in an unusable state.\n\n");
	fprintf(stderr, "You can override this protection by adding the --allow-run-as-root\n");
	fprintf(stderr, "option to your cmd line. However, we reiterate our strong advice\n");
	fprintf(stderr, "against doing so - please do so at your own risk.\n");
	fprintf(stderr, "--------------------------------------------------------------------------\n");
	exit(1);
	}