Improve build process embedded manifests

This commit changes the way the build of manifests is triggered by
making smarter use of the capabilities of Make. The result should be
that the manifests are only regenerated if:

1. There is no `cmd/flux/manifests/` directory.
2. There have been made changes to the YAML files in the `manifests/`
   directory that are newer than the files in `cmd/flux/manifests/`.

Signed-off-by: Hidde Beydals <hello@hidde.co>

.github/workflows/bootstrap.yaml

@@ -30,7 +30,7 @@ jobs:
         uses: fluxcd/pkg//actions/kustomize@main
       - name: Build
         run: |
-          make build-manifests
+          make cmd/flux/manifests
           go build -o /tmp/flux ./cmd/flux
       - name: Set outputs
         id: vars

.github/workflows/release.yaml

@@ -30,7 +30,7 @@ jobs:
         uses: fluxcd/pkg//actions/kustomize@main
       - name: Generate manifests
         run: |
-          make build-manifests
+          make cmd/flux/manifests
           ./manifests/scripts/bundle.sh ./output manifests.tar.gz
           kustomize build ./manifests/install > ./output/install.yaml
       - name: Run GoReleaser

.github/workflows/scan.yaml

@@ -31,7 +31,7 @@ jobs:
         uses: fluxcd/pkg//actions/kustomize@main
       - name: Build manifests
         run: |
-          make build-manifests
+          make cmd/flux/manifests
       - name: Run Snyk to check for vulnerabilities
         uses: snyk/actions/golang@master
         continue-on-error: true

Makefile

@@ -1,4 +1,7 @@
 VERSION?=$(shell grep 'VERSION' cmd/flux/main.go | awk '{ print $$4 }' | tr -d '"')
+EMBEDDED_MANIFESTS_TARGET=cmd/flux/manifests
+
+rwildcard=$(foreach d,$(wildcard $(addsuffix *,$(1))),$(call rwildcard,$(d)/,$(2)) $(filter $(subst *,%,$(2)),$(d)))
 
 all: test build
 
@@ -11,13 +14,13 @@ fmt:
 vet:
 	go vet ./...
 
-test: build-manifests tidy fmt vet docs
+test: $(EMBEDDED_MANIFESTS_TARGET) tidy fmt vet docs
 	go test ./... -coverprofile cover.out
 
-build-manifests:
+$(EMBEDDED_MANIFESTS_TARGET): $(call rwildcard,manifests/,*.yaml *.json)
 	./manifests/scripts/bundle.sh
 
-build:
+build: $(EMBEDDED_MANIFESTS_TARGET)
 	CGO_ENABLED=0 go build -o ./bin/flux ./cmd/flux
 
 install:
@@ -25,7 +28,7 @@ install:
 
 .PHONY: docs
 docs:
-	rm docs/cmd/*
+	rm -rf docs/cmd/*
 	mkdir -p ./docs/cmd && go run ./cmd/flux/ docgen
 
 install-dev: