Docker image doesn't build on Raspberry Pi

The Dockerfile is using alpine:3.5 to build minificpp, which doesn't exist for ARM. Updating the alpine version to 3.7 will allow it to build on both x86 and ARM. 3.8 is the latest version, however alpine 3.8 uses libressl version 2.7, which isn't compatible with libarchive 3.3.2. . libarchive 3.3.3 resolves the issue - https://github.com/libarchive/libarchive/pull/1005