build.sh: define TMP_DIR relative to OUT_DIR

Using /tmp breaks concurrent builds trying to use /tmp/kernel-headers.
Isolate builds and make them self-contained by using a tmp directory
relative to OUT_DIR.

Change-Id: I4a435bbc9a5532c5890278b0d742b5bd1d837513
Signed-off-by: Matthias Maennich <maennich@google.com>
1 file changed