"  /usr/bin/c++ -march=athlon64 -O2 -pipe -msse3 -fPIC -Wl,-O1 -ldl -lmpi
  CMakeFiles/cmTryCompileExec.dir/testCXXCompiler.cxx.o -o cmTryCompileExec
  -rdynamic


  /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/../../../../x86_64-pc-linux-gnu/bin/ld:
  cannot find -lmpi
"

USE="mpi" may help?

-- 
Marcin Rybarski

GPG 1024D/26C836EB
Key fingerprint = 1506 8442 D232 101F 15AD  C332 2054 80CD 26C8 36EB