The "libffi" directory holds a copy of libffi version 3.3.
The libffi code is distributed under an LGPL-compatible license.

Changes to the source in this copy:

 * Commented out `__attribute__((deprecated))` for `ffi_java_...` to
   avoid warnings when compiling libffi itself

 * Added $CPPFLAGS to use of $CC in "configure.host"

 * Added preprocessor conditionals for Go closures in "ffi_darwin.c"

 * Adjusted "config.guess" to detect Mac OS AArch64

 * Disable FFI_EXEC_TRAMPOLINE_TABLE for Mac OS AArch64, since
   we use pthread_jit_write_protect_np() in the Racket wrapper
