graphics/colmap: unbreak OPENMP on -CURRENT i386 after r499662

ld: error: undefined symbol: __atomic_load

referenced by PoissonRecon.cpp

PoissonRecon.cpp.o:(.omp_outlined.) in archive lib/PoissonRecon/libpoisson_recon.a

ld: error: undefined symbol: __atomic_compare_exchange

referenced by PoissonRecon.cpp

PoissonRecon.cpp.o:(.omp_outlined.) in archive lib/PoissonRecon/libpoisson_recon.a

Reported by: pkg-fallout