docs: add Make as build system (elastic#886)

* docs: fix list item

* docs: explain that APM is enabled for Helm and Metricbeat

* docs: update permalink for BEAT_VERSION

* docs: add Make as build system

e2e/README.md

@@ -56,6 +56,9 @@ Each module will define its own file for specificacions, adding specific feature
 
 ## Technology stack
 
+## Build system
+The test framework makes use of `Make` to prepare the environment to run the `godog` tests. Although it's still possible using the `godog` binary to run the test suites and scenarios, we recommend using the proper `Make` goals, in particular the [`functional-test` goal](https://github.com/elastic/e2e-testing/blob/70b1d3ddaf39567aeb4c322054b93ad7ce53e825/e2e/Makefile#L70). We also provide [a set of example goals](https://github.com/elastic/e2e-testing/blob/70b1d3ddaf39567aeb4c322054b93ad7ce53e825/e2e/Makefile#L108) with different use cases for running most common scenarios.
+
 ### Docker containers
 The services supported by some of the test suites in this framework will be started in the form of Docker containers. To manage the life cycle of those containers in test time we are going to use [`Testcontainers`](https://testcontainers.org), a set of libraries to simplify the usage of the Docker client, attaching container life cycles to the tests, so whenever the tests finish, the containers will stop in consequence.
 
@@ -118,7 +121,7 @@ We are going to enumerate the variables that will affect the product versions us
 > Related to this compatibility matrix too, it's also remarkable that Kibana **Fleet** plugin should not allow to enroll an agent with a version higher than kibana (See https://github.com/elastic/kibana/blob/fed9a4fddcc0087ee9eca6582a2a84e001890f08/x-pack/test/fleet_api_integration/apis/agents/enroll.ts#L99).
 
 #### Fleet
-- `BEAT_VERSION`. Set this environment variable to the proper version of the Elastic Agent to be used in the current execution. Default: See https://github.com/elastic/e2e-testing/blob/0446248bae1ff604219735998841a21a7576bfdd/.ci/Jenkinsfile#L36
+- `BEAT_VERSION`. Set this environment variable to the proper version of the Elastic Agent to be used in the current execution. Default: See https://github.com/elastic/e2e-testing/blob/70b1d3ddaf39567aeb4c322054b93ad7ce53e825/.ci/Jenkinsfile#L44
 - `ELASTIC_AGENT_DOWNLOAD_URL`. Set this environment variable if you know the bucket URL for an Elastic Agent artifact generated by the CI, i.e. for a pull request. It will take precedence over the `BEAT_VERSION` variable. Default empty: See https://github.com/elastic/e2e-testing/blob/0446248bae1ff604219735998841a21a7576bfdd/.ci/Jenkinsfile#L35
 - `ELASTIC_AGENT_STALE_VERSION`. Set this environment variable to the proper version of the Elastic Agent to be used in the upgrade tests, representing the version to be upgraded. Default: See https://github.com/elastic/e2e-testing/blob/b8d0cb09d575f90f447fe3331b6df0a185c01c89/.ci/Jenkinsfile#L38
 
@@ -129,13 +132,16 @@ We are going to enumerate the variables that will affect the product versions us
 - `HELM_KUBERNETES_VERSION`. Set this environment variable to the proper version of Kubernetes to be used in the current execution. Default: See https://github.com/elastic/e2e-testing/blob/0446248bae1ff604219735998841a21a7576bfdd/.ci/Jenkinsfile#L46
 
 #### Metricbeat
-- `BEAT_VERSION`. Set this environment variable to the proper version of the Metricbeat to be used in the current execution. Default: See https://github.com/elastic/e2e-testing/blob/0446248bae1ff604219735998841a21a7576bfdd/.ci/Jenkinsfile#L42
+- `BEAT_VERSION`. Set this environment variable to the proper version of the Metricbeat to be used in the current execution. Default: See https://github.com/elastic/e2e-testing/blob/70b1d3ddaf39567aeb4c322054b93ad7ce53e825/.ci/Jenkinsfile#L44
 
 ### Environment variables affecting the build
 The following environment variables affect how the tests are run in both the CI and a local machine.
 
 - `ELASTIC_APM_ACTIVE`: Set this environment variable to `true` if you want to send instrumentation data to our CI clusters. When the tests are run in our CI, this variable will always be enabled. Default value: `false`.
-`- ELASTIC_APM_ENVIRONMENT`: Set this environment variable to `ci` to send APM data to Elastic Cloud. Otherwise, the framework will spin up local APM Server and Kibana instances. For the CI, it will read credentials from Vault. Default value: `local`.
+
+>"ELASTIC_APM_ACTIVE" only affects Helm and Metricbeat test suites.
+
+- `ELASTIC_APM_ENVIRONMENT`: Set this environment variable to `ci` to send APM data to Elastic Cloud. Otherwise, the framework will spin up local APM Server and Kibana instances. For the CI, it will read credentials from Vault. Default value: `local`.
 - `SKIP_SCENARIOS`: Set this environment variable to `false` if it's needed to include the scenarios annotated as `@skip` in the current test execution. Default value: `true`.
 - `BEATS_LOCAL_PATH`: Set this environment variable to the base path to your local clone of Beats if it's needed to use the binary snapshots produced by your local build instead of the official releases. The snapshots will be fetched from the `${BEATS_LOCAL_PATH}/${THE_BEAT}/build/distributions` local directory. This variable is intended to be used by Beats developers, when testing locally the artifacts generated its own build. Default: empty.
 - `BEATS_USE_CI_SNAPSHOTS`: Set this environment variable to `true` if it's needed to use the binary snapshots produced by Beats CI instead of the official releases. The snapshots will be downloaded from a bucket in Google Cloud Storage. This variable is used by the Beats repository, when testing the artifacts generated by the packaging job. Default: `false`.