Q:

Gitlab CI/CD with Terraform and 3rd party plugin

I'm provisioning resources on AWS as well as on a 3rd party system via a custom provider. On my local environment, it works fine (as I have downloaded and compiled the 3rd party provider).
As a next step, I’m trying to run a Gitlab pipeline with Terraform.The AWS part works because it's a Terrafrom registered provider, however the 3rd party part fails (because it's not a registered Terraform provider). 
When I try to run a Gitlab pipeline, it complains with an error and advises the following

In the latter case, the plugin must be installed manually by locating
  and downloading a suitable distribution package and placing the
  plugin’s executable file in the following directory:
  terraform.d/plugins/linux_amd64

The .gitlab-ci.yml file I have is the following:
image:
  name: hashicorp/terraform:light
  entrypoint:
    - '/usr/bin/env'
    - 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'

before_script:
  - rm -rf .terraform
  - terraform --version
  - export AWS_ACCESS_KEY
  - export AWS_SECRET_KEY
  - terraform init

stages:
  - validate
  - plan
  - apply

validate:
  stage: validate
  script:
    - terraform validate

plan:
  stage: plan
  script:
    - terraform plan -out "planfile"
  dependencies:
    - validate
  artifacts:
    paths:
      - planfile

apply:
  stage: apply
  script:
    - terraform apply -input=false "planfile"
  dependencies:
    - plan
  when: manual

I see an image is used called 'hashicorp/terraform:light'. Should I create a docker image based on this image with the 3rd party provider already in?
EDIT1
It's clear a custom image is required. I used the idea from rflume below and used the following Dockerfile to build the image.
# Multi-Stage builds require Docker Engine 17.05 or higher

# Build ACI provider
FROM ubuntu:bionic-20190515 as builder

ENV HOME /root
ENV GOPATH $HOME/go
ENV GOBIN $GOPATH/bin

RUN apt update &&\
    apt install -yqq software-properties-common \
    git \
    wget \
    unzip \
    gcc \
    perl \
    go-dep \
    make \
    build-essential &&\
    add-apt-repository ppa:longsleep/golang-backports &&\
    apt-get update &&\
    apt-get install -y golang-go &&\
    mkdir -p $GOPATH/src/github.com/terraform-providers &&\
    wget -O $HOME/terraform-provider-aci.zip https://github.com/ciscoecosystem/terraform-provider-aci/archive/master.zip &&\
    cd $GOPATH/src/github.com/terraform-providers/ &&\
    unzip $HOME/terraform-provider-aci.zip -d . &&\
    mv terraform-provider-aci-master \
    terraform-provider-aci-v1.0.0

WORKDIR $GOPATH/src/github.com/terraform-providers/terraform-provider-aci-v1.0.0

RUN dep ensure
RUN make build

# Build the actual image
FROM hashicorp/terraform:0.11.14

ENV GOBIN /root/go/bin
ENV PATH $GOBIN:$PATH

RUN mkdir -p /root/.terraform.d/plugins

COPY --from=builder /root/go/bin/terraform-provider-aci-v1.0.0 $GOBIN/terraform-provider-aci-v1.0.0

ENTRYPOINT ["/bin/sh", "-c"]

A:

The solution was to create an image with the custom provider already in.
FROM hashicorp/terraform:full

ENV GOPATH /go

RUN mkdir -p $GOPATH/src/github.com/ciscoecosystem
WORKDIR $GOPATH/src/github.com/ciscoecosystem
RUN git clone https://github.com/ciscoecosystem/terraform-provider-aci.git $GOPATH/src/github.com/ciscoecosystem/terraform-provider-aci
RUN git clone https://github.com/ciscoecosystem/aci-go-client.git $GOPATH/src/github.com/ciscoecosystem/aci-go-client
RUN apk add --no-cache build-base

WORKDIR $GOPATH/src/github.com/ciscoecosystem/terraform-provider-aci

RUN make build

WORKDIR $GOPATH

ENTRYPOINT ["terraform"]

