Go makefile with cross compilation

Makefile

default: build

OS=$(shell uname | tr [:upper:] [:lower:])
PLATFORMS=linux darwin freebsd
PKG_NAME=$(shell glide name)
APP_NAME=$(shell basename $(PKG_NAME))
APP_VERSION=$(shell git describe --tags --always)
BRANCH?=$(shell git rev-parse --abbrev-ref HEAD)

BUILD_DIR?=build
BUILD_TYPE?=develop
ifeq ($(BUILD_TYPE),develop)
	BUILD_FLAGS=
else
	BUILD_FLAGS=-ldflags "-X main.version=$(APP_VERSION) -s -w"
endif

compile=GOOS=$(1) GOARCH=amd64 go build $(BUILD_FLAGS) -o $(2) $(3)
pack=tar -C $(1) -jcf $(2) $(3)

BIN_PATTERN=$(BUILD_DIR)/%/$(BRANCH)/$(APP_NAME)
PACK_FLAT_DIR=$(BUILD_DIR)/_pkg
# useful to produce packages organized in folders. E.g. S3
PACK_FLAT_PATTERN=$(PACK_FLAT_DIR)/$(APP_NAME)-%-$(APP_VERSION).tar.bz2
# useful to produce packages for flat displaying. E.g. Github releases
PACK_NEST_PATTERN=$(BIN_PATTERN).tar.bz2

.PHONY: run build pack fpack clean

# Compile and run for current OS only
run: $(OS); $(<:%=$(BIN_PATTERN))

# Compile for all platforms
build: $(PLATFORMS)

# Compile the specified platform. E.g. `make linux`
$(PLATFORMS): %: $(BIN_PATTERN)

$(BIN_PATTERN): cmd/server.go
	$(call compile,$*,$@,$<)

# Package binaries for all platforms
pack: $(PLATFORMS:%=pack-%) | clean-bin

fpack: $(PLATFORMS:%=fpack-%) | clean-bin

# Create package for specified platform. E.g. `make pack-linux`
$(PLATFORMS:%=pack-%): pack-%: $(PACK_NEST_PATTERN)

# Optional way of creating packages in a flat hierarchy. E.g. `make fpack-linux`
$(PLATFORMS:%=fpack-%): fpack-%: $(PACK_FLAT_PATTERN)

$(PACK_FLAT_PATTERN): $(BIN_PATTERN)
	@mkdir -p $(PACK_FLAT_DIR)
	$(call pack,$(^D),$(PACK_FLAT_DIR)/$(@F),$(^F))

$(PACK_NEST_PATTERN): $(BIN_PATTERN)
	$(call pack,$(^D),$@,$(^F))

clean: clean-bin clean-pack clean-fpack

clean-bin:
	-rm -f $(PLATFORMS:%=$(BIN_PATTERN))

clean-pack:
	-rm -f $(PLATFORMS:%=$(PACK_NEST_PATTERN))

clean-fpack:
	-rm -rf $(PACK_FLAT_DIR)

Not an expert Makefile-maker but this works for my current go needs