tcmode: use /tmp/sourcery-$LOGNAME for TMPDIR

Work around the bad interaction between cs-license and pseudo by shoving all
the temporary files into a subdir by the user's original logname.

JIRA: SB-1905

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Merge pull request #36 from MentorEmbedded/sb-1905

tcmode: use /tmp/sourcery-$LOGNAME for TMPDIR