Docker build doesn't work on MacOS

[ashokkjag]

The dockerfile simply copies the natively build binary, which doesn't work in case of docker on MacOS.

# stripe-mock > master > make build
go build -mod=vendor -o stripe-mock
# stripe-mock > master > docker build -t "stripe-mock" .
[+] Building 1.3s (8/8) FINISHED
 => [internal] load build definition from Dockerfile                                                                                                                         0.0s
 => => transferring dockerfile: 264B                                                                                                                                         0.0s
 => [internal] load .dockerignore                                                                                                                                            0.0s
 => => transferring context: 97B                                                                                                                                             0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                                                                             0.5s
 => [1/3] FROM docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1                                                       0.0s
 => [internal] load build context                                                                                                                                            0.5s
 => => transferring context: 21.24MB                                                                                                                                         0.5s
 => CACHED [2/3] RUN apk --no-cache add ca-certificates                                                                                                                      0.0s
 => [3/3] COPY stripe-mock /bin/stripe-mock                                                                                                                                  0.1s
 => exporting to image                                                                                                                                                       0.1s
 => => exporting layers                                                                                                                                                      0.0s
 => => writing image sha256:401df59925dbbb7447b73ca87619a63aeda6e36cf9db906ec680f727d8271512                                                                                 0.0s
 => => naming to docker.io/library/stripe-mock                                                                                                                               0.0s
# stripe-mock > master > docker run --rm stripe-mock:latest
exec /bin/stripe-mock: exec format error

[richardm-stripe]

Fixed by #430