'referencia indefinida a' errores al intentar compilar con Make

Tenía un Makefile en funcionamiento que compiló con éxito y construyó un programa básico para alternar y LED en mi placa stm32-h103. Desde entonces he intentado agregar y usar FreeRTOS en mi programa. He agregado las rutas de FreeRTOS en mi Makefile, sin embargo, cuando ejecuto make, obtengo los siguientes errores.

src/app.a(startup.o):(.isr_vectors+0x2c): undefined reference to 'vPortSVCHandler'
src/app.a(startup.o):(.isr_vectors+0x38): undefined reference to 'xPortPendSVHandler'
src/app.a(startup.o):(.isr_vectors+0x3c): undefined reference to 'xPortSysTickHandler'
src/app.a(main.o): In function 'main':
/home/matthew/Work/22_ARM-Firmware/HomeAutomationControllerPrototype/src/main.c:36: undefined reference to 'xTaskGenericCreate'
/home/matthew/Work/22_ARM-Firmware/HomeAutomationControllerPrototype/src/main.c:37: undefined reference to 'vTaskStartScheduler'
collect2: error: ld returned 1 exit status

Soy muy nuevo en Makefiles, así que no estoy seguro de qué más debo agregar para compilar el código.

Mis dos archivos make son:

Makefile.common

TOP=$(shell readlink -f "$(dir $(lastword $(MAKEFILE_LIST)))")
PROGRAM=main
LIBDIR=$(TOP)/libs
FREERTOSDIR=$(TOP)/src/FreeRTOS/Source

#Adust the following line to the library in use
STMLIB=$(LIBDIR)/STM32F10x_StdPeriph_Lib_V3.6.1/Libraries

#Adjust TypeOfMCU in use, see CMSIS file "stm32f10x.h"
#STM32F103RBT (128KB FLASH, 20KB RAM) --> STM32F10X_MD
TypeOfMCU=STM32F10X_MD
#STM32F103RET (512KB FLASH, 64KB RAM) --> STM32F10X_HD
#TypeOfMCU=STM32F10X_HD

TC=arm-none-eabi
CC=$(TC)-gcc
LD=$(TC)-ld -v
OBJCOPY=$(TC)-objcopy
AR=$(TC)-ar
GDB=$(TC)-gdb

INCLUDE=-I$(TOP)/inc
INCLUDE+=-I$(STMLIB)/CMSIS/Include
INCLUDE+=-I$(STMLIB)/CMSIS/Device/ST/STM32F10x/Include
INCLUDE+=-I$(STMLIB)/CMSIS/Device/ST/STM32F10x/Source/Templates
INCLUDE+=-I$(STMLIB)/STM32F10x_StdPeriph_Driver/inc
INCLUDE+=-I$(STMLIB)/STM32_USB-FS-Device_Driver/inc
INCLUDE+=-I$(FREERTOSDIR)/include
INCLUDE+=-I$(FREERTOSDIR)/portable/GCC/ARM_CM3
INCLUDE+=-I$(TOP)/src


COMMONFLAGS=-g -mcpu=cortex-m3 -mthumb
COMMONFLAGSlib=$(COMMONFLAGS)

#Commands for general Makefile and src Makefile
ifeq ($(OptSRC),0)
    COMMONFLAGS+=-O0
    InfoTextSrc=src (no optimize, -O0)
else ifeq ($(OptSRC),1)
    COMMONFLAGS+=-O1
    InfoTextSrc=src (optimize time+ size+, -O1)
else ifeq ($(OptSRC),2)
    COMMONFLAGS+=-O2
    InfoTextSrc=src (optimize time++ size+, -O2)
else ifeq ($(OptSRC),s)
    COMMONFLAGS+=-Os
    InfoTextSrc=src (optimize size++, -Os) 
else ifeq ($(OptSRC),3)
    COMMONFLAGS+=-O3
    InfoTextSrc=src (full optimize, -O3)
else
    COMMONFLAGS+=-O3
    CFLAGS += -D RELEASE_PUBLIC
    InfoTextSrc=src (full optimize and readout protected, -O4)
endif
CFLAGS+=$(COMMONFLAGS) -Wall -Werror $(INCLUDE)
CFLAGS+=-D $(TypeOfMCU)
CFLAGS+=-D VECT_TAB_FLASH

#Commands for libs Makefile
ifeq ($(OptLIB),0)
    COMMONFLAGSlib+=-O0
    InfoTextLib=libs (no optimize, -O0)
else ifeq ($(OptLIB),1)
    COMMONFLAGSlib+=-O1
    InfoTextLib=libs (optimize time+ size+, -O1)
else ifeq ($(OptLIB),2)
    COMMONFLAGSlib+=-O2
    InfoTextLib=libs (optimize time++ size+, -O2)
else ifeq ($(OptLIB),s)
    COMMONFLAGSlib+=-Os
    InfoTextLib=libs (optimize size++, -Os)
else
    COMMONFLAGSlib+=-O3
InfoTextLib=libs (full optimize, -O3)
endif
CFLAGSlib+=$(COMMONFLAGSlib) -Wall -Werror $(INCLUDE)
CFLAGSlib+=-D $(TypeOfMCU)
CFLAGSlib+=-D VECT_TAB_FLASH

Y mi src Makefile

# src Makefile

include ../Makefile.common

OBJS+=startup.o
OBJS+=main.o

all: src

src: app.a

app.a: $(OBJS)
    $(AR) cr app.a $(OBJS)

.PHONY: src clean tshow

clean:
    rm -f app.a $(OBJS)