Build manager binary in a modular way

Allow overriding CGO_ENABLED value, static flag, and exporting GOEXPERIMENT

hack/build.sh

@@ -1,5 +1,4 @@
-#!/bin/bash
-set -ex
+#!/bin/bash -ex
 
 GIT_VERSION=$(git describe --always --tags || true)
 VERSION=${CI_UPSTREAM_VERSION:-${GIT_VERSION}}
@@ -9,8 +8,29 @@ BUILD_DATE=$(date --utc -Iseconds)
 
 mkdir -p bin
 
-LDFLAGS="-s -w "
-LDFLAGS+="-X github.com/medik8s/node-maintenance-operator/version.Version=${VERSION} "
-LDFLAGS+="-X github.com/medik8s/node-maintenance-operator/version.GitCommit=${COMMIT} "
-LDFLAGS+="-X github.com/medik8s/node-maintenance-operator/version.BuildDate=${BUILD_DATE} "
-GOFLAGS=-mod=vendor CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="${LDFLAGS}" -o bin/manager main.go
+# first value must not be quoted
+LDFLAGS_VALUE="-X github.com/medik8s/node-maintenance-operator/version.Version=${VERSION}"
+# additional values must be quoted when used with GOFLAGS!
+LDFLAGS_VALUE+=" \"-w\""
+LDFLAGS_VALUE+="-X github.com/medik8s/node-maintenance-operator/version.GitCommit=${COMMIT} "
+LDFLAGS_VALUE+="-X github.com/medik8s/node-maintenance-operator/version.BuildDate=${BUILD_DATE}"
+# allow override for static flag
+LDFLAGS_STATIC="${LDFLAGS_STATIC:-" \"-s\""}"
+LDFLAGS_VALUE+="${LDFLAGS_STATIC}"
+# must be single quoted for use in GOFLAGS
+LDFLAGS="'-ldflags=${LDFLAGS_VALUE}'"
+
+# add ldflags to goflags
+export GOFLAGS+=" ${LDFLAGS}"
+echo "goflags: ${GOFLAGS}"
+
+# allow override and use zero by default- static linking
+export CGO_ENABLED=${CGO_ENABLED:-0}
+echo "cgo: ${CGO_ENABLED}"
+
+# export in case it was set
+if [ ! -z "${GOEXPERIMENT}" ]; then
+    export GOEXPERIMENT= $GOEXPERIMENT
+fi
+
+GOOS=linux GOARCH=amd64 go build -o bin/manager main.go