don't use a *-tcc to compile *.S files for ARM*

A tcc for ARM* don't have an assembler. This is partial reverse of the commit
  build-libtcc1-by-tcc: use a new tcc to compile a libtcc1.c and alloca.S

lib/Makefile

@@ -21,9 +21,11 @@ ifndef TARGET # native library
  else
  ifeq ($(ARCH),arm)
   TARGET = arm
+  XCC = $(CC)
  else
  ifeq ($(ARCH),arm64)
   TARGET = arm64
+  XCC = $(CC)
  else
  endif
  endif