* Remove excess layer creation
This is an antipattern in Docker.
* Remove build tools once build is complete
Leaving them around is not necessary and expands the image size 5x
* Make check works with libonig installed
* Compiles statically (needs libonig to be built rather than installed)
* Valgrind doesn't work with the use of TLS in jq so it's disabled -- this
might be a FIXME situation; I'm not familiar enough with valgrind to
say whether this is expected
* Make entrypoint be the jq binary so that the image can also be used
to run jq in environments where you don't want to or can't install
jq (such as CoreOS).
