make check failed due to 32/64 bits problem

[Torbjorn Granlund]

Paul Zimmermann <Paul.Zimmermann at loria.fr> writes:

  Note that with GMP >= 4.2.3 and MPFR >= 2.4.0 (which should be soon out),
  MPFR will automagically get CC/CFLAGS from GMP.
  
That might be very helpful to all users, in particular the many new
users that arrived with gcc.

How does it do that?  

-- 
Torbjörn