* use docker buildx for multiplatform build
* more verbose echos about behavior in build/push step
* echo instead of comment
---------
Co-authored-by: Jason Baker <jbaker@gosonar.com>
```
Build a docker image
Usage:
./build.sh [<tag> | --help]
Argument:
<tag> Build an image for the given graphhopper repository tag [default: master]
Option:
--help Print this message
```