/tmp is backed by swap. You ran out of swap on your system: swap -lh shows: swapfile dev swaplo blocks free /dev/zvol/dsk/rpool/swap 182,2 4K 639M 639M
swap -sh shows total: 285M allocated + 109M reserved = 394M used, 868M available See section 2.1.2 of http://hub.opensolaris.org/bin/view/Community+Group+on/devref_2. The build environment swap requirement is 1GB minimum and 2GB recommended.
