$ docker image build --pull --tag example .
Sending build context to Docker daemon  75.26kB
Step 1/3 : FROM alpine
latest: Pulling from library/alpine
Digest: sha256:ca1c944a4f8486a153024d9965aafbe24f5723c1d5c02f4964c045a16d19dc54
Status: Image is up to date for alpine:latest
 ---> 4d90542f0623
Step 2/3 : WORKDIR /root
 ---> Using cache
 ---> f1df3106650a
Step 3/3 : RUN set -ex     && wget -q -O mkcert https://github.com/FiloSottile/mkcert/releases/download/v1.3.0/mkcert-v1.3.0-linux-arm     && chmod +x mkcert     && ./mkcert -install     && ./mkcert localhost
 ---> Running in 7dce34e8bf2a
+ wget -q -O mkcert https://github.com/FiloSottile/mkcert/releases/download/v1.3.0/mkcert-v1.3.0-linux-arm
+ chmod +x mkcert
+ ./mkcert -install
Created a new local CA at "/root/.local/share/mkcert" �
Installing to the system store is not yet supported on this Linux � but Firefox and/or Chrome/Chromium will still work.
You can also manually install the root certificate at "/root/.local/share/mkcert/rootCA.pem".

+ ./mkcert localhost
Using the local CA at "/root/.local/share/mkcert" ✨
Warning: the local CA is not installed in the system trust store! ⚠️
Run "mkcert -install" to avoid verification errors ‼️

Created a new certificate valid for the following names �
 - "localhost"

The certificate is at "./localhost.pem" and the key at "./localhost-key.pem" ✅

Removing intermediate container 7dce34e8bf2a
 ---> 8f5c4f5e7940
Successfully built 8f5c4f5e7940
Successfully tagged example:latest

Running with gitlab-runner 12.0.0-rc1 (58d8360f)
  on docker-auto-scale 0277ea0f
Using Docker executor with image docker:stable ...
Starting service docker:stable-dind ...
Pulling docker image docker:stable-dind ...
Using docker image sha256:12adad4e12e25288e665131d5235d98a8edf2a39d26679dabbe2728442729e26 for docker:stable-dind ...
Waiting for services to be up and running...
Pulling docker image docker:stable ...
Using docker image sha256:805bea199b249bfed61cdcd7cdbfe240ee998d51f59bbf365674a15b619f5a86 for docker:stable ...
Running on runner-0277ea0f-project-13015620-concurrent-0 via runner-0277ea0f-srm-1561404020-8e640368...
Fetching changes with git depth set to 50...
Initialized empty Git repository in /builds/anthonymastrean/mkcert-example/.git/
Created fresh repository.
From https://gitlab.com/anthonymastrean/mkcert-example
 * [new branch]      master     -> origin/master
Checking out 61c5932f as master...

Skipping Git submodules setup
$ docker image build --pull --tag example .
Sending build context to Docker daemon  47.62kB

Step 1/3 : FROM alpine
latest: Pulling from library/alpine
921b31ab772b: Pulling fs layer
921b31ab772b: Verifying Checksum
921b31ab772b: Download complete
921b31ab772b: Pull complete
Digest: sha256:ca1c944a4f8486a153024d9965aafbe24f5723c1d5c02f4964c045a16d19dc54
Status: Downloaded newer image for alpine:latest
 ---> 4d90542f0623
Step 2/3 : WORKDIR /root
 ---> Running in 104eadb1c574
Removing intermediate container 104eadb1c574
 ---> 4de722b6deac
Step 3/3 : RUN set -ex     && wget -q -O mkcert https://github.com/FiloSottile/mkcert/releases/download/v1.3.0/mkcert-v1.3.0-linux-arm     && chmod +x mkcert     && ./mkcert -install     && ./mkcert localhost
 ---> Running in 6c027ecfa62a
+ wget -q -O mkcert https://github.com/FiloSottile/mkcert/releases/download/v1.3.0/mkcert-v1.3.0-linux-arm
+ chmod +x mkcert
+ ./mkcert -install
/bin/sh: ./mkcert: not found
The command '/bin/sh -c set -ex     && wget -q -O mkcert https://github.com/FiloSottile/mkcert/releases/download/v1.3.0/mkcert-v1.3.0-linux-arm     && chmod +x mkcert     && ./mkcert -install     && ./mkcert localhost' returned a non-zero code: 127
ERROR: Job failed: exit code 127