mktemp: add -p/--tmpdir argument

This matches other mktemp implementations, including OpenBSD and GNU.
The -p option can be used to provide a tmpdir prefix for specified
templates.  Precedence works out like so:

-t flag:
- $TMPDIR
- -p directory
- /tmp

Implied -t flag (no arguments or only -d flag):
- -p directory
- $TMPDIR
- /tmp

Some tests have been added for mktemp(1) in the process.

Reviewed by:	imp (earlier version), wosch
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D37121

1 files changed, 2 insertions, 0 deletions

diff --git a/etc/mtree/BSD.tests.dist b/etc/mtree/BSD.tests.dist
index 1a00c13f78ba..5fbcd3c31669 100644
--- a/etc/mtree/BSD.tests.dist
+++ b/etc/mtree/BSD.tests.dist
@@ -1060,6 +1060,8 @@
         ..
         mkimg
         ..
+        mktemp
+        ..
         ncal
         ..
         opensm