mxqd: Use environment MXQ_JOB_TMPDIR

It might be usefull for a  script to know, if it has a job-specific
temporary filesystem or not.

If the job was submitted with --tmpdir then set both MXQ_JOB_TMPDIR and
TMPDIR to the path of the temporary space.

If a program is run without --tmpdir or outside of mxqd, then TMPDIR
usually points to some (non-private) temporary space as well, but
MXQ_JOB_TMPDIR will not be set.

mxqd.c

@@ -791,7 +791,11 @@ static int init_child_process(struct mxq_group_list *glist, struct mxq_job *job)
     if (group->job_tmpdir_size == 0) {
         mx_setenv_forever("TMPDIR", server->initial_tmpdir);
     } else {
-        mx_setenvf_forever("TMPDIR", "%s/%lu", MXQ_JOB_TMPDIR_MNTDIR, job->job_id);
+        char *mxq_job_tmpdir;
+        mx_asprintf_forever(&mxq_job_tmpdir, "%s/%lu", MXQ_JOB_TMPDIR_MNTDIR, job->job_id);
+        mx_setenv_forever("MXQ_JOB_TMPDIR", mxq_job_tmpdir);
+        mx_setenv_forever("TMPDIR", mxq_job_tmpdir);
+        free(mxq_job_tmpdir);
     }
     fh = open("/proc/self/loginuid", O_WRONLY|O_TRUNC);
     if (fh == -1) {

mxqsub.c

@@ -71,7 +71,7 @@ static void print_usage(void)
     "\n"
     "  -j, --threads=NUMBER     set number of threads       (default: 1)\n"
     "  -m, --memory=SIZE        set amount of memory        (default: 2G)\n"
-    "      --tmpdir=SIZE        set size of TMPDIR          (default: 0)\n"
+    "      --tmpdir=SIZE        set size of MXQ_JOB_TMPDIR  (default: 0)\n"
     "\n"
     "        [SIZE] may be suffixed with a combination of T, G and M\n"
     "               to specify tebibytes, gibibytes and mebibytes.\n"