Makefile for building Unity3d C# managed DLL on Mac

Makefile

# Boilarplate: Makefile for building Unity3d C# managed DLL on Mac
# 
# [Usage]
# If Unity is installed in the default directory /Applications/Unity/Unity.app, simply:
# $ make
# Or either:
# $ UNITY_NAME=UnityXXX make
# $ UNITY_DIR=/Applications/UnityXXX/UnityYYY.app make
#
# [library directory layout]
# +-- (library dir)
#     |
#     +---src  (contains source files)
#     |   |
#     |   +-- ...
#     |
#     +---bin  (built module goes here)

UNITY_NAME = Unity544
UNITY_DIR  = /Applications/$(UNITY_NAME)/$(UNITY_NAME).app

# -- Unity provided files
# mono compiler
SMCS             = $(shell find $(UNITY_DIR)/Contents -type f -name smcs | grep /bin/smcs)
# UnityEngine.dll
UNITY_ENGINE_DLL = $(UNITY_DIR)/Contents/Managed/UnityEngine.dll
# UnityEditor.dll
UNITY_EDITOR_DLL = $(UNITY_DIR)/Contents/Managed/UnityEditor.dll

# directories
SRC_DIR     = src
BUILD_DIR   = bin
TARGET_NAME = MyLibrary.dll

# Target DLL path
BUILD_TARGET = $(BUILD_DIR)/$(TARGET_NAME)

# source files
SRC = $(shell find $(SRC_DIR) -name '*.cs')

# build flags
SMCS_FLAGS  = -define:UNITY_5_3_OR_NEWER;RELEASE

# -- check existance of required files

ifeq ($(SMCS),)
$(error Mono compiler 'smcs' is not found in $(UNITY_DIR))
endif

ifeq ($(wildcard $(UNITY_ENGINE_DLL)),)
$(error UnityEngine.dll is not found as $(UNITY_DIR)/Managed/UnityEngine.dll)
endif

ifeq ($(wildcard $(UNITY_EDITOR_DLL)),)
$(error UnityEditor.dll is not found as $(UNITY_DIR)/Managed/UnityEditor.dll)
endif

.PHONY: all build

all: build

build: $(BUILD_TARGET)

$(BUILD_TARGET): $(SRC)
# create the build target directory
	$(shell install -d $(BUILD_DIR))
# build
	$(SMCS) -r:$(UNITY_ENGINE_DLL) -r:$(UNITY_EDITOR_DLL) -define:$(SMCS_FLAGS) -target:library -out:$(BUILD_TARGET) $(SRC)
	@echo built: $@

If you have error like Makefile:66: *** multiple target patterns. Stop., check the code file that indents are made with TAB(SPC is wrong in Makefile).