refactor: separate directory for thirdparty code

Makefile

@@ -6,15 +6,20 @@ LIB_FILENAME ?= libvieter.a
 BUILD_DIR ?= build
 SRC_DIR ?= src
 TEST_DIR ?= test
-INC_DIRS ?= include
+3RDPARTY_DIR ?= thirdparty
+INCLUDE_DIR ?= include
 
+INC_DIRS ?= $(INCLUDE_DIR) $(3RDPARTY_DIR)/include
 LIB := $(BUILD_DIR)/$(LIB_FILENAME)
 
 SRCS != find '$(SRC_DIR)' -iname '*.c'
-SRCS_H != find $(INC_DIRS) -iname '*.h'
+SRCS_H != find $(INCLUDE_DIR) -iname '*.h'
 SRCS_TEST != find '$(TEST_DIR)' -iname '*.c'
+SRCS_3RDPARTY != find '$(3RDPARTY_DIR)/src' -iname '*.c'
 
-OBJS := $(SRCS:%=$(BUILD_DIR)/%.o)
+$(info ${SRCS})
+
+OBJS := $(SRCS:%=$(BUILD_DIR)/%.o) $(SRCS_3RDPARTY:%=$(BUILD_DIR)/%.o)
 OBJS_TEST := $(SRCS_TEST:%=$(BUILD_DIR)/%.o)
 DEPS := $(SRCS:%=$(BUILD_DIR)/%.d) $(SRCS_TEST:%=$(BUILD_DIR)/%.d)
 
@@ -51,6 +56,9 @@ $(BUILD_DIR)/$(SRC_DIR)/%.c.o: $(SRC_DIR)/%.c
 	mkdir -p $(dir $@)
 	$(CC) $(VIETERCFLAGS) -c $< -o $@
 
+$(BUILD_DIR)/$(3RDPARTY_DIR)/src/%.c.o: $(3RDPARTY_DIR)/src/%.c
+	mkdir -p $(dir $@)
+	$(CC) $(VIETERCFLAGS) -c $< -o $@
 
 # =====TESTING=====
 .PHONY: test