While I'm at it, I ran a few benchmarks (each one is just asking gltfpack to process a specific glTF file with different options that shift the processing bottleneck) using gcc/clang and all three optimization options.

Broad conclusions:

- Switch to clang
- Use Os or O2 as appropriate for perf/speed tradeoff

All of these are bottlenecked in individual very hot functions; for large C++ applications aka sprawling web of nonsense Os might see perf benefits.

*: -O2 build time is higher due to -g