Compiling Crystal on ARM is not very common. This is how I did it in order to compile and test CNF Conformance on ARM.
I use a lot of different cloud providers and I just wanted to throw out there for those not familiar with Vultr.com, they got a promotion going on for new signups, get $50 in credit to try out their solutions.
The one thing that makes Vultr.com stand out from some of the others is they provide smaller instances that start at $2.50 a month for IPV6 only connections but also have $3.50 a month instances that include IPV4 connections.
These smaller VM's are great ways to do testing, rolling out clustered VMs, etc.
If you're looking for a cheaper solution for cloud infrastructure, these people have been great.