remove unused variables in makefile

Makefile

@@ -8,20 +8,17 @@ CFLAGS = -g -I$(INC_DIR) -Wall
 LDFLAGS = -lm
 TEST_SRC = $(wildcard $(TEST_DIR)/*.c)
 TARGET_SRC = $(wildcard $(TARGET_DIR)/*.c)
-# Strip file path so each demo source gets a target,
-# e.g. examples/01_demo.c -> 01_demo
-TARGETS = $(patsubst $(TARGET_DIR)/%.c, %, $(TARGET_SRC))
 
 # If `test` is passed as a cmd argument, extend flags to handle unit tests 
 ifeq ($(MAKECMDGOALS), test)
-    CFLAGS += -DRUN_UNIT_TESTS
     SRC = $(wildcard $(SRC_DIR)/*.c)
     TARGETS = $(patsubst $(TEST_DIR)/%.c,%,$(TEST_SRC))
     TARGET_DIR = test
-    TARGET = $(TARGETS)
 	OBJECTS = $(SRC:%.c=%.o) $(TEST_SRC)
 else
-    TARGET = $(TARGETS)
+    # Strip file path so each demo source gets a target,
+    # e.g. examples/01_demo.c -> 01_demo
+    TARGETS = $(patsubst $(TARGET_DIR)/%.c, %, $(TARGET_SRC))
     SRC = $(wildcard $(SRC_DIR)/*.c)
 	OBJECTS = $(SRC:%.c=%.o)
 endif