Add arm64 (AArch64) as a target architecture.

lib/Makefile

@@ -28,6 +28,11 @@ ifndef TARGET # native library
  ifeq ($(ARCH),arm)
   TARGET = arm
   XCC = $(CC)
+ else
+ ifeq ($(ARCH),arm64)
+  TARGET = arm64
+ else
+ endif
  endif
  endif
  endif
@@ -49,6 +54,7 @@ X86_64_O = libtcc1.o alloca86_64.o
 ARM_O = libtcc1.o armeabi.o alloca-arm.o
 WIN32_O = $(I386_O) crt1.o wincrt1.o dllcrt1.o dllmain.o chkstk.o
 WIN64_O = $(X86_64_O) crt1.o wincrt1.o dllcrt1.o dllmain.o chkstk.o
+ARM64_O = lib-arm64.o
 
 # build TCC runtime library to contain PIC code, so it can be linked
 # into shared libraries
@@ -86,6 +92,11 @@ ifeq "$(TARGET)" "arm"
  OBJ = $(addprefix $(DIR)/,$(ARM_O))
  TGT = -DTCC_TARGET_ARM
  XCC ?= $(TCC) -B$(TOP)
+else
+ifeq "$(TARGET)" "arm64"
+ OBJ = $(addprefix $(DIR)/,$(ARM64_O))
+ TGT = -DTCC_TARGET_ARM64
+ XCC ?= $(TCC) -B$(TOP)
 else
  $(error libtcc1.a not supported on target '$(TARGET)')
 endif
@@ -93,6 +104,7 @@ endif
 endif
 endif
 endif
+endif
 
 XFLAGS = $(CPPFLAGS) $(CFLAGS) $(PICFLAGS) $(TGT)