use BUILDTAGS env variable for customized build with go build tags

Author: its-felix

collector/Makefile

@@ -7,7 +7,7 @@ LAYER_NAME:=otel-collector
 OTELCOL_VERSION="UNSET" # run recipe set-otelcol-version to get this
 GIT_SHA=$(shell git rev-parse HEAD)
 GOARCH ?= amd64
-GOBUILD=GO111MODULE=on CGO_ENABLED=0 installsuffix=cgo go build -trimpath
+GOBUILD=GO111MODULE=on CGO_ENABLED=0 installsuffix=cgo go build -trimpath$(if ${BUILDTAGS}, -tags "${BUILDTAGS}",)
 BUILD_INFO_IMPORT_PATH=main
 
 LDFLAGS=-ldflags "-s -w -X $(BUILD_INFO_IMPORT_PATH).GitHash=$(GIT_SHA) -X $(BUILD_INFO_IMPORT_PATH).Version=$(OTELCOL_VERSION) \

collector/README.md

@@ -29,7 +29,7 @@ Once this build-tag is present, you need provide additional build-tags to includ
 
 Each available component can also be included explicitly by using its specific build-tag. For a full-list of available components, have a look into the [lambdacomponents](./collector/lambdacomponents) package.
 
-As an example, the full build command including the following components:
+As an example, the full command to publish OpenTelemetry Collector Lambda layer in your AWS account and get its ARN including the following components:
 - All receivers
 - All processors
 - No extensions
@@ -38,7 +38,7 @@ As an example, the full build command including the following components:
 
 would be the following:
 ```shell
-go build -tags "lambdacomponents.custom,lambdacomponents.receiver.all,lambdacomponents.processor.all,lambdacomponents.exporter.otlphttp,lambdacomponents.connector.spanmetrics"
+cd collector && BUILDTAGS="lambdacomponents.custom,lambdacomponents.receiver.all,lambdacomponents.processor.all,lambdacomponents.exporter.otlphttp,lambdacomponents.connector.spanmetrics" make publish-layer
 ```
 
 ### Adding additional options