Support env -u e.g. unsetting vars under OSX

Makefile

@@ -28,6 +28,7 @@ GO_BUILD_INSTALL_DEPS=-i
 GO_BUILD_TAGS='netgo unsafe'
 GO_BUILD_FLAGS=$(GO_BUILD_INSTALL_DEPS) -ldflags "-extldflags \"-static\" -X main.version=$(SCOPE_VERSION)" -tags $(GO_BUILD_TAGS)
 
+
 all: $(SCOPE_EXPORT)
 
 $(DOCKER_DISTRIB):
@@ -67,6 +68,15 @@ $(SCOPE_EXE) $(RUNSVINIT) lint tests shell prog/static.go: $(SCOPE_BACKEND_BUILD
 
 else
 
+UNAME := $(shell uname)
+ifeq ($(UNAME), Darwin)
+	UNSET_GOARCH_GOOS=unset GOARCH GOOS;
+	UNSET_GOGC=unset GOGC;
+else
+	UNSET_GOARCH_GOOS=env -u GOGC -u GOOS
+	UNSET_GOGC=env -u GOGC
+endif
+
 $(SCOPE_EXE): $(SCOPE_BACKEND_BUILD_UPTODATE)
 	time $(GO) build $(GO_BUILD_FLAGS) -o $@ ./$(@D)
 	@strings $@ | grep cgo_stub\\\.go >/dev/null || { \
@@ -79,12 +89,12 @@ $(SCOPE_EXE): $(SCOPE_BACKEND_BUILD_UPTODATE)
 	    }
 
 %.codecgen.go: $(CODECGEN_EXE)
-	rm -f $@ && env -u GOARCH -u GOOS $(GO) build -i -tags $(GO_BUILD_TAGS) ./$(@D) # workaround for https://github.com/ugorji/go/issues/145
-	cd $(@D) && env -u GOARCH -u GOOS $(GO_ENVS) $(shell pwd)/$(CODECGEN_EXE) -rt $(GO_BUILD_TAGS) -u -o $(@F) $(notdir $(call GET_CODECGEN_DEPS,$(@D)))
+	rm -f $@ && $(UNSET_GOARCH_GOOS) $(GO) build -i -tags $(GO_BUILD_TAGS) ./$(@D) # workaround for https://github.com/ugorji/go/issues/145
+	cd $(@D) && $(UNSET_GOARCH_GOOS) $(GO_ENVS) $(shell pwd)/$(CODECGEN_EXE) -rt $(GO_BUILD_TAGS) -u -o $(@F) $(notdir $(call GET_CODECGEN_DEPS,$(@D)))
 
 $(CODECGEN_EXE): $(CODECGEN_DIR)/*.go
 	mkdir -p $(@D)
-	env -u GOARCH -u GOOS $(GO) build -i -tags $(GO_BUILD_TAGS) -o $@ ./$(CODECGEN_DIR)
+	$(UNSET_GOARCH_GOOS) $(GO) build -i -tags $(GO_BUILD_TAGS) -o $@ ./$(CODECGEN_DIR)
 
 $(RUNSVINIT): $(SCOPE_BACKEND_BUILD_UPTODATE)
 	time $(GO) build $(GO_BUILD_FLAGS) -o $@ ./$(@D)
@@ -93,7 +103,7 @@ shell: $(SCOPE_BACKEND_BUILD_UPTODATE)
 	/bin/bash
 
 tests: $(SCOPE_BACKEND_BUILD_UPTODATE)
-	env -u GOGC $(GO_ENVS) ./tools/test -no-go-get
+	$(UNSET_GOGC) $(GO_ENVS) ./tools/test -no-go-get
 
 lint: $(SCOPE_BACKEND_BUILD_UPTODATE)
 	./tools/lint .