makefile: add LDFLAGS environment variable. LDFLAGS default to empty string ("")

Author: nvanheuverzwijn

Makefile

@@ -1,5 +1,6 @@
 OS = darwin freebsd linux openbsd
 ARCHS = 386 arm amd64 arm64
+LDFLAGS =
 
 .DEFAULT_GOAL := help
 
@@ -10,7 +11,7 @@ help:
 all: build release release-windows
 
 build: deps ## Build the project
-	go build
+	go build -ldflags="$(LDFLAGS)"
 
 release: clean deps ## Generate releases for unix systems
 	@for arch in $(ARCHS);\
@@ -19,7 +20,7 @@ release: clean deps ## Generate releases for unix systems
 		do \
 			echo "Building $$os-$$arch"; \
 			mkdir -p build/webhook-$$os-$$arch/; \
-			GOOS=$$os GOARCH=$$arch go build -o build/webhook-$$os-$$arch/webhook; \
+			GOOS=$$os GOARCH=$$arch go build -ldflags="$(LDFLAGS)" -o build/webhook-$$os-$$arch/webhook; \
 			tar cz -C build -f build/webhook-$$os-$$arch.tar.gz webhook-$$os-$$arch; \
 		done \
 	done
@@ -29,7 +30,7 @@ release-windows: clean deps ## Generate release for windows
 	do \
 		echo "Building windows-$$arch"; \
 		mkdir -p build/webhook-windows-$$arch/; \
-		GOOS=windows GOARCH=$$arch go build -o build/webhook-windows-$$arch/webhook.exe; \
+		GOOS=windows GOARCH=$$arch go build -ldflags="$(LDFLAGS)" -o build/webhook-windows-$$arch/webhook.exe; \
 		tar cz -C build -f build/webhook-windows-$$arch.tar.gz webhook-windows-$$arch; \
 	done