Generate fields.yaml when building filebeat docker image

ravelin/Dockerfile

@@ -1,3 +1,17 @@
+# TODO: Move to internal golang image
+FROM golang:1.21.2-alpine3.18 as fields_builder
+RUN apk add build-base linux-headers python3 py3-pip && \
+    pip3 install --upgrade setuptools
+COPY . /filebeat
+WORKDIR /filebeat/ravelin
+RUN sh install-mage.sh && \
+    tar -zxvf mage.tar.gz && \
+    chmod +x mage && \
+    mv mage /usr/local/bin/mage && \
+    apk add make
+RUN make build
+
+# TODO: Move to internal filebeat image
 FROM docker.elastic.co/beats/filebeat:8.9.2
 USER root
 
@@ -10,5 +24,5 @@ COPY x-pack/filebeat/module/gcp/cloud_armor /usr/share/filebeat/module/gcp/cloud
 COPY x-pack/filebeat/module/gcp/cilium /usr/share/filebeat/module/gcp/cilium
 
 # Copying scoped fields
-COPY ravelin/fields.yml fields.yml
+COPY --from=fields_builder /filebeat/ravelin/fields.yml fields.yml
 USER filebeat

ravelin/Makefile

@@ -3,8 +3,3 @@ build:
 	@cd ../filebeat && mage update
 	@echo "[-] filtering fields"
 	@python3 filter-fields.py
-	@echo "[-] building custom docker image"
-	@cd .. && docker build --platform linux/amd64 -t europe-docker.pkg.dev/ravelin-builds/container/sec-tools/filebeat:8.9.2 -f ravelin/Dockerfile .
-
-publish:
-	@docker push europe-docker.pkg.dev/ravelin-builds/container/sec-tools/filebeat:8.9.2