Add automatic TMPDIR setup/teardown to GNU Make

We now guarantee TMPDIR will be defined on a per build rule basis. It'll
be an absolute path. It'll be secure and unique. It'll be rm -rf'd after
the last shell script line in your build rule is executed. If $TMPDIR is
already defined, then it'll be created as a subdirectory of your $TMPDIR
and then replace the variable with the new definition. The Landlock Make
repository will be updated with examples shortly after this change which
shall be known as Landlock Make 1.1.1.

See #530

third_party/make/debug.h

@@ -15,6 +15,8 @@ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 You should have received a copy of the GNU General Public License along with
 this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include "libc/intrin/likely.h"
+
 #define DB_NONE         (0x000)
 #define DB_BASIC        (0x001)
 #define DB_VERBOSE      (0x002)
@@ -26,7 +28,7 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 extern int db_level;
 
-#define ISDB(_l)    ((_l)&db_level)
+#define ISDB(_l)    UNLIKELY((_l)&db_level)
 
 /* When adding macros to this list be sure to update the value of
    XGETTEXT_OPTIONS in the po/Makevars file.  */