[racket] Compiling Racket on Maemo 5

The main obstacle was that operations like `raco make' and `raco setup'
needed SHA-1 hashing from OpenSSL via the FFI.

I've adjusted several things so that `make' and `make install' can
work when the FFI is disabled:

 * A new `file/sha1' library ports Eric Knauel's implementation of
   SHA-1 to Racket.

 * The `openssl/sha1' library falls back to `file/sha1' when the FFI
   isn't supported or when OpenSSL isn't available.

 * The built-in `#%foreign' library exports stubs for all of the names
   that are normally exported when the FFI is disabled. It's just
   enough to let `openssl/sha1' load and fall back to `file/sha1'.

Hashing by `file/sha1' is about 500 times as slow as OpenSSL hashing,
but it should work well enough for `raco setup'.


At Tue, 13 Jul 2010 10:19:11 -0600, Kevin Tew wrote:
> Ok I tried compiling with your configure line myself.
> I had to make an additional change to get racket/racketcgc to build.
> 
> the 3m  variant still doesn't build do to more reliance on the ffi 
> during xform.
> setup is also going to try to use the ffi.
> 
> We have added additional dependencies on the ffi (foreign function 
> interface) and need to decide if we are going to support building 
> without it.
> My guess is that is possible but will require some engineering effort.
> 
> Kevin