Makefile的帮助:没有规则可使目标

CC = g++
CFLAGS = -Wall

RM = /bin/rm -rf
BIN_DIR = 

ifeq "$(DEBUG)" "1"
BIN_DIR = Debug
else
BIN_DIR = Release
endif

OBJS = \
$(BIN_DIR)/Unit.o

$(BIN_DIR)/%.o: src/%.c
    @echo Building "$@"
    @g++ -c "$<" -o"$@"

all: $(OBJS)
clean:
    $(RM) $(BIN_DIR)

.PHONY: all clean

但是,当我尝试构建我的项目时,它会给我一个错误:

make: *** No rule to make target 'Release/Unit.o', needed by 'all'. Stop.

我对从头开始编写makefile很陌生,所以这可能是一个愚蠢的问题,但是任何帮助都是值得感谢的!