anchor.diff:  
   (defun local-environment ()
     #+linux "-gnu"
  -  #-linux "")
  +  #+android "-androideabi"
  +  #+(not (or linux android)) "")
   
   (defun local-arch ()
     (string+ (local-cpu) (local-vendor) (local-os) (local-environment)))
  
positive.code:     "x86_64-unknown-freebsd"
      "i386-unknown-openbsd"
      "x86_64-unknown-openbsd"
      "arm-pc-linux-gnu"))
  
   ;; c2ffi
  
negative.code:   #+(not (or linux windows darwin)) "-unknown")
  
  (defun local-os ()
    #+(or linux android) "-linux"
    #+windows "-windows-msvc"
    #+darwin "-darwin9"
    #+freebsd "-freebsd"
  