Add ARM spinlock

Makefile

@@ -1,11 +1,14 @@
-CC = arm-none-eabi-gcc
-AS = arm-none-eabi-as
-LD = arm-none-eabi-ld
+TOOLCHAIN = arm-none-eabi
+
+CC = $(TOOLCHAIN)-gcc
+AS = $(TOOLCHAIN)-as
+LD = $(TOOLCHAIN)-ld
 CPU = -mcpu=cortex-m4
 THUMB = -mthumb
 
 LDFLAGS = -T linker.ld
 CFLAGS = $(CPU) $(THUMB) -I libc/ -I ./
+CC_SYMBOLS = -DTOOLCHAIN_GCC_ARM
 
 QEMU = qemu-system-arm
 BOARD = netduinoplus2
@@ -13,7 +16,7 @@ BOARD = netduinoplus2
 # Output file
 TARGET = main.elf
 # Source files
-SRCS = os/main.c os/process.c os/scheduler.c os/alloc.c os/delay.c os/driver/usart.c libc/library.c tasks/tasks.c
+SRCS = os/main.c os/process.c os/scheduler.c os/alloc.c os/delay.c os/driver/usart.c os/sync/spinlock.c libc/library.c tasks/tasks.c
 # Object files
 OBJS = $(SRCS:.c=.o)