title: GCC cant find GMP, MPFR and MPC libraries
body: <p>I am trying to cross-compile GCC on Mac OS 10.5.7. I used this command to configure GCC after installing GMP, MPFR, and MPC:</p>
  
  <pre><code>../gcc-4.5.0/configure --target=$i586-elf --prefix=/usr/local/cross \
      --disable-nls \
      --enable-languages=c,c++,fortran,java,objc,obj-c++,treelang,ada \
      --without-headers --with-libiconv-prefix=/opt/local --with-gmp=/usr/local \
      --with-mpfr=/usr/local --with-mpc=/usr/local
  </code></pre>
  
  <p>I got this error:</p>
  
  <pre><code>checking for the correct version of gmp.h... buggy but acceptable
  checking for the correct version of mpfr.h... yes
  checking for the correct version of mpc.h... yes
  checking for the correct version of the gmp/mpfr/mpc libraries... no
  configure: error: Building GCC requires GMP 4.2+, MPFR 2.3.1+ and MPC 0.8.0+.
  Try the --with-gmp, --with-mpfr and/or --with-mpc options to specify
  their locations.  Source code for these libraries can be found at
  their respective hosting sites as well as at
  ftp://gcc.gnu.org/pub/gcc/infrastructure/.  See also
  http://gcc.gnu.org/install/prerequisites.html for additional info.  If
  you obtained GMP, MPFR and/or MPC from a vendor distribution package,
  make sure that you have installed both the libraries and the header
  files.  They may be located in separate packages.
  </code></pre>
  
  <p>Why could GCC find the headers for GMP, MPFR, and MPC but not the libraries?</p>