icecompr: fix missed 'make clean' artifact
icecompr: fix missed 'make clean' artifact

Signed-off-by: Austin Seipp <48c905ac3851f382b914247d97dd93273d5ff555@pobox.com>

SymbiFlow/icestorm,SymbiFlow/icestorm,SymbiFlow/icestorm,SymbiFlow/icestorm