refactor: let go.mod manage mage version (#5414)

* refactor: let go.mod manage mage version

drop hardcoded version and use whatever version is specified in go.mod
When calling go install without an explicit version the one in go.mod
is used.

* lint: remove unused variables

* lint: remove unused variables

Author: kruskall

.buildkite/scripts/common.sh

@@ -6,9 +6,6 @@ if [[ -z "${WORKSPACE-""}" ]]; then
     WORKSPACE=$(git rev-parse --show-toplevel)
     export WORKSPACE
 fi
-if [[ -z "${SETUP_MAGE_VERSION-""}" ]]; then
-    SETUP_MAGE_VERSION="1.15.0"
-fi
 if [[ -z "${SETUP_GVM_VERSION-""}" ]]; then
     SETUP_GVM_VERSION="v0.5.2" # https://github.com/andrewkroh/gvm/issues/44#issuecomment-1013231151
 fi
@@ -54,7 +51,6 @@ mage() {
     go version
     if ! [ -x "$(type -P mage | sed 's/mage is //g')" ];
     then
-        echo "installing mage ${SETUP_MAGE_VERSION}"
         make mage
     fi
     pushd "$WORKSPACE"

Dockerfile.skaffold

@@ -7,11 +7,11 @@ ARG AGENT_IMAGE="docker.elastic.co/beats/elastic-agent"
 FROM ${crossbuild_image}:${GO_VERSION}-main-debian8 as build
 ARG DEV="true"
 ARG SNAPSHOT="true"
-RUN go install github.com/magefile/mage@v1.15.0
 WORKDIR /elastic-agent/
 COPY go.mod go.sum /elastic-agent/
 RUN go mod download
 COPY . /elastic-agent/
+RUN go install github.com/magefile/mage
 RUN mage golangcrossBuild
 RUN git rev-parse HEAD | cut -c 1-6 > .build_hash.txt
 

Makefile

@@ -3,7 +3,6 @@ COVERAGE_DIR=$(BUILD_DIR)/coverage
 BEATS?=elastic-agent
 PROJECTS= $(BEATS)
 PYTHON_ENV?=$(BUILD_DIR)/python-env
-MAGE_VERSION     ?= v1.15.0
 MAGE_PRESENT     := $(shell mage --version 2> /dev/null | grep $(MAGE_VERSION))
 MAGE_IMPORT_PATH ?= github.com/magefile/mage
 export MAGE_IMPORT_PATH
@@ -12,11 +11,11 @@ export MAGE_IMPORT_PATH
 .PHONY: mage
 mage:
 ifndef MAGE_PRESENT
-	@echo Installing mage $(MAGE_VERSION).
-	@go install ${MAGE_IMPORT_PATH}@$(MAGE_VERSION)
+	@echo Installing mage.
+	@go install ${MAGE_IMPORT_PATH}
 	@-mage -clean
 else
-	@echo Mage $(MAGE_VERSION) already installed.
+	@echo Mage already installed.
 endif
 
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