make elevation decompression configurable

[derEremit]

https://github.com/gis-ops/docker-valhalla/blob/78e925913b97e401f81608fa24f13ab91924e880/scripts/configure_valhalla.sh#L225C1-L225C86

I for one only need the elevation tiles for building the final tiles. And am more limited by space then cpu time.
so that would help me to be able to set decompress to false or also to lz4

https://github.com/valhalla/valhalla/blob/a01d80ce737083a733ab203c44fbadb3642fe9b7/scripts/valhalla_build_elevation#L123

[chrstnbwnkl]

Yep, makes sense. I'd be happy to review a PR!