Build static library during Makefile build.

Makes it easier to use SPIRV-Cross as an API.
Add some subsection in README about this.

Makefile

@@ -1,27 +1,37 @@
 TARGET := spirv-cross
-SOURCES := $(wildcard *.cpp)
+
+SOURCES := $(wildcard spirv_*.cpp)
+CLI_SOURCES := main.cpp
+
 OBJECTS := $(SOURCES:.cpp=.o)
-DEPS := $(OBJECTS:.o=.d)
+CLI_OBJECTS := $(CLI_SOURCES:.cpp=.o)
+
+STATIC_LIB := lib$(TARGET).a
+
+DEPS := $(OBJECTS:.o=.d) $(CLI_OBJECTS:.o=.d)
 
 CXXFLAGS += -std=c++11 -Wall -Wextra
 
 ifeq ($(DEBUG), 1)
-	CXXFLAGS += -O0 -gdwarf-2
+	CXXFLAGS += -O0
 else
-	CXXFLAGS += -O2 -gdwarf-2
+	CXXFLAGS += -O2
 endif
 
 all: $(TARGET)
 
 -include $(DEPS)
 
-$(TARGET): $(OBJECTS)
-	$(CXX) -o $@ $(OBJECTS) $(LDFLAGS)
+$(TARGET): $(CLI_OBJECTS) $(STATIC_LIB)
+	$(CXX) -o $@ $(CLI_OBJECTS) $(STATIC_LIB) $(LDFLAGS)
+
+$(STATIC_LIB): $(OBJECTS)
+	$(AR) rcs $@ $(OBJECTS)
 
 %.o: %.cpp
 	$(CXX) -c -o $@ $< $(CXXFLAGS) -MMD
 
 clean:
-	rm -f $(TARGET) $(OBJECTS) $(DEPS)
+	rm -f $(TARGET) $(OBJECTS) $(CLI_OBJECTS) $(STATIC_LIB) $(DEPS)
 
 .PHONY: clean

README.md

@@ -79,6 +79,12 @@ int main()
 }
 ```
 
+#### Integrating SPIRV-Cross in a custom build system
+
+To add SPIRV-Cross to your own codebase, just copy the source and header files from root directory
+and build the relevant .cpp files you need. Make sure to build with C++11 support, e.g. `-std=c++11` in GCC and Clang.
+Alternatively, the Makefile generates a libspirv-cross.a static library during build that can be linked in.
+
 ### Creating a SPIR-V file from GLSL with glslang
 
 ```