[ci] Remove plugin build

The platform plugin builds were used at a time when functional tests
were, at times, run from source.

This is mostly no longer a requirement. There are two remaining cypress
scripts that I updated to use the build instead.

.buildkite/scripts/download_build_artifacts.sh

@@ -11,7 +11,6 @@ if [[ "${KIBANA_BUILD_ID:-}" != "false" ]]; then
     cd "$WORKSPACE"
 
     download_artifact kibana-default.tar.gz . --build "${KIBANA_BUILD_ID:-$BUILDKITE_BUILD_ID}"
-    download_artifact kibana-default-plugins.tar.gz . --build "${KIBANA_BUILD_ID:-$BUILDKITE_BUILD_ID}"
 
     mkdir -p "$KIBANA_BUILD_LOCATION"
     tar -xzf kibana-default.tar.gz -C "$KIBANA_BUILD_LOCATION" --strip=1
@@ -24,7 +23,5 @@ if [[ "${KIBANA_BUILD_ID:-}" != "false" ]]; then
     fi
 
     cd "$KIBANA_DIR"
-
-    tar -xzf ../kibana-default-plugins.tar.gz
   fi
 fi

.buildkite/scripts/steps/build_kibana.sh

@@ -4,6 +4,4 @@ set -euo pipefail
 
 .buildkite/scripts/bootstrap.sh
 .buildkite/scripts/build_kibana.sh
-.buildkite/scripts/build_kibana_plugins.sh
-.buildkite/scripts/post_build_kibana_plugins.sh
 .buildkite/scripts/post_build_kibana.sh

.buildkite/scripts/steps/functional/defend_workflows_burn.sh

@@ -4,9 +4,7 @@ set -euo pipefail
 
 source .buildkite/scripts/steps/functional/common.sh
 
-.buildkite/scripts/bootstrap.sh
-node scripts/build_kibana_platform_plugins.js
-
+export KIBANA_INSTALL_DIR=${KIBANA_BUILD_LOCATION}
 export JOB=kibana-defend-workflows-cypress
 
 buildkite-agent meta-data set "${BUILDKITE_JOB_ID}_is_test_execution_step" 'false'

.buildkite/scripts/steps/functional/defend_workflows_serverless_burn.sh

@@ -4,9 +4,7 @@ set -euo pipefail
 
 source .buildkite/scripts/steps/functional/common.sh
 
-.buildkite/scripts/bootstrap.sh
-node scripts/build_kibana_platform_plugins.js
-
+export KIBANA_INSTALL_DIR=${KIBANA_BUILD_LOCATION}
 export JOB=kibana-defend-workflows-serverless-cypress
 
 buildkite-agent meta-data set "${BUILDKITE_JOB_ID}_is_test_execution_step" 'false'