xilinx SDK编译问题，无法编译出.elf文件，请问依赖变量为什么为空的？

helloworld.elf: $(OBJS) ../src/lscript.ld $(USER_OBJS)7 x4 O* [. N$ K5 \; i, _1 c% X# F8 w" U
@Echo 'Building target: $@'6 ~. I. l/ Z% q; ?# E- B3 b
@echo 'Invoking: ARM v7 gcc linker'
, z( [* W6 `! H5 f/ V6 h9 H5 i7 k8 Zarm-none-eabi-gcc -mcpu=cortex-a9 -mfpu=vfpv3 -mfloat-abi=hard -Wl,-build-id=none -specs=Xilinx.spec -Wl,-T -Wl,../src/lscript.ld -L../../helloworld_bsp/ps7_cortexa9_0/lib -o "helloworld.elf" $(OBJS) $(USER_OBJS) $(LIBS)
- R  y6 J/ x; a0 U@echo 'Finished building target: $@'
' c# G& w; P$ |- O3 I@echo ' '

LIBS := -Wl,--start-group,-lxil,-lgcc,-lc,--end-group

LD_SRCS :=
/ |9 [! [6 M& W* v0 POBJ_SRCS := # _3 _) f6 ?; j- z
S_SRCS := 2 g0 S: o0 M7 c9 J# d0 g7 V
C_SRCS :=
' g/ ]/ S, H* k$ `# N8 G! _S_UPPER_SRCS :=
9 ~( a8 O  f% h* Y- e1 BO_SRCS := , h' {. E. W0 i8 X* z
EXECUTABLES := 2 k* Q  R" z7 G6 p9 \0 |9 r
OBJS :=
% e8 F, c9 j! j# O$ p& P8 fS_UPPER_DEPS :=
& a% x+ b9 h) D% r& O8 |  J3 _C_DEPS :=
( J7 k; }% w- PELFSIZE :=

SUBDIRS := \
' p! `+ ?- @" j/ u% F! K5 psrc \