fix potentially broken support for macos

macOS support is broken for users who rely on the Makefile to install
libgit2 for them. libgit2.1.1.dylib could not be dynamically linked at runtime
because it couldn't be found. This patch makes the following changes to
the Makefile:
1) Respects the user's PKG_CONFIG_PATH present in the env so that both
   libgit2.pc and openssl.pc are discoverable.
2) Embeds the required rpath in the binary at compile time, so that
   libgit2.1.1.dylib can be found at runtime. For more info see:
   fluxcd#515 (comment)
Signed-off-by: Sanskar Jaiswal <[email protected]>

Signed-off-by: pa250194 <[email protected]>

Makefile

@@ -39,7 +39,12 @@ endif
 
 ifeq ($(shell uname -s),Darwin)
 	LIBGIT2 := $(LIBGIT2_LIB_PATH)/libgit2.$(LIBGIT2_VERSION).dylib
+	HAS_BREW := $(shell brew --version 2>/dev/null)
+ifdef HAS_BREW
+	HAS_OPENSSL := $(shell brew --prefix [email protected])
 endif
+endif
+
 
 # API (doc) generation utilities
 CONTROLLER_GEN_VERSION ?= v0.5.0
@@ -52,23 +57,53 @@ else
 GOBIN=$(shell go env GOBIN)
 endif
 
+ifeq ($(strip ${PKG_CONFIG_PATH}),)
+	MAKE_PKG_CONFIG_PATH = $(LIBGIT2_LIB_PATH)/pkgconfig
+else
+	MAKE_PKG_CONFIG_PATH = ${PKG_CONFIG_PATH}:$(LIBGIT2_LIB_PATH)/pkgconfig
+endif
+
+ifdef HAS_OPENSSL
+	MAKE_PKG_CONFIG_PATH := $(MAKE_PKG_CONFIG_PATH):$(HAS_OPENSSL)/lib/pkgconfig
+endif
+
 all: build
 
 build: $(LIBGIT2) ## Build manager binary
-	PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig/ \
+ifeq ($(shell uname -s),Darwin)
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
+	CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
+	go build -o bin/manager main.go
+else
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
 	go build -o bin/manager main.go
+endif
 
 test: $(LIBGIT2) test-api  ## Run tests
+ifeq ($(shell uname -s),Darwin)
 	LD_LIBRARY_PATH=$(LIBGIT2_LIB_PATH) \
-	PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig/ \
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
+	CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
 	go test ./... -coverprofile cover.out
+else
+	LD_LIBRARY_PATH=$(LIBGIT2_LIB_PATH) \
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
+	go test ./... -coverprofile cover.out
+endif
 
 test-api: ## Run api tests
 	cd api; go test ./... -coverprofile cover.out
 
 run: $(LIBGIT2) generate fmt vet manifests  ## Run against the configured Kubernetes cluster in ~/.kube/config
+ifeq ($(shell uname -s),Darwin)
 	LD_LIBRARY_PATH=$(LIBGIT2_LIB_PATH) \
+	CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
 	go run ./main.go
+else
+	LD_LIBRARY_PATH=$(LIBGIT2_LIB_PATH) \
+	go run ./main.go
+endif
+
 
 install: manifests  ## Install CRDs into a cluster
 	kustomize build config/crd | kubectl apply -f -
@@ -102,9 +137,16 @@ fmt:  ## Run go fmt against code
 	cd api; go fmt ./...
 
 vet: $(LIBGIT2)	## Run go vet against code
-	PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig \
+ifeq ($(shell uname -s),Darwin)
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
+	CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
+	go vet ./...
+	cd api; go vet ./...
+else
+	PKG_CONFIG_PATH=$(MAKE_PKG_CONFIG_PATH) \
 	go vet ./...
 	cd api; go vet ./...
+endif
 
 generate: controller-gen  ## Generate API code
 	cd api; $(CONTROLLER_GEN) object:headerFile="../hack/boilerplate.go.txt" paths="./..."