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/source-controller#515 (comment)

Signed-off-by: Sanskar Jaiswal <[email protected]>

Makefile

@@ -47,6 +47,10 @@ 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
 
 # Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
@@ -56,6 +60,16 @@ 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
+
 TEST_CRDS := controllers/testdata/crds
 
 # Log level for `make run`
@@ -88,19 +102,39 @@ ${CACHE}/imagepolicies_${REFLECTOR_VER}.yaml:
  -o ${CACHE}/imagepolicies_${REFLECTOR_VER}.yaml
 
 test: $(LIBGIT2) test-api test_deps generate fmt vet manifests api-docs ## Run tests
+ifeq ($(shell uname -s),Darwin)
  LD_LIBRARY_PATH=$(LIBGIT2_LIB_PATH) \
- PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig/:$(PKG_CONFIG_PATH) \
+ PKG_CONFIG_PATH=$(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
 
 manager: $(LIBGIT2) generate fmt vet ## Build manager binary
- PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig/:$(PKG_CONFIG_PATH) \
+ifeq ($(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=$(MAKE_PKG_CONFIG_PATH) \
+ CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
  go build -o bin/manager main.go
+endif
+
 
 run: $(LIBGIT2) generate fmt vet manifests # Run against the configured Kubernetes cluster in ~/.kube/config
+ifeq ($(shell uname -s),Darwin)
+ CGO_LDFLAGS="-Wl,-rpath,$(LIBGIT2_LIB_PATH)" \
  go run ./main.go --log-level=${LOG_LEVEL} --log-encoding=console
+else
+ go run ./main.go --log-level=${LOG_LEVEL} --log-encoding=console
+endif
 
 install: manifests ## Install CRDs into a cluster
  kustomize build config/crd | kubectl apply -f -
@@ -133,9 +167,17 @@ fmt: ## Run go fmt against code
  cd api; go fmt ./...
 
 vet: $(LIBGIT2) ## Run go vet against code
- PKG_CONFIG_PATH=$(LIBGIT2_LIB_PATH)/pkgconfig:$(PKG_CONFIG_PATH) \
+ifeq ($(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 code
  cd api; $(CONTROLLER_GEN) object:headerFile="../hack/boilerplate.go.txt" paths="./..."