>>> Emerging (3 of 53) sci-libs/flann-1.6.11
 * flann-1.6.11-src.zip RMD160 SHA1 SHA256 size ;-) ...                  [ ok ]
>>> Unpacking source...
>>> Unpacking flann-1.6.11-src.zip to /var/tmp/portage/sci-libs/flann-1.6.11/work
>>> Source unpacked in /var/tmp/portage/sci-libs/flann-1.6.11/work
>>> Preparing source in /var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11-src ...
>>> Source prepared.
>>> Configuring source in /var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11-src ...
>>> Working in BUILD_DIR: "/var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11_build"
cmake --no-warn-unused-cli -C /var/tmp/portage/sci-libs/flann-1.6.11/temp/gentoo_common_config.cmake -DCMAKE_INSTALL_PREFIX=/usr -DBUILD_C_BINDINGS=ON -DBUILD_MATLAB_BINDINGS=OFF -DBUILD_PYTHON_BINDINGS=ON -DUSE_mpi=ON -DUSE_MPI=ON -DUSE_Mpi=ON -DCMAKE_BUILD_TYPE=Gentoo -DCMAKE_INSTALL_DO_STRIP=OFF -DCMAKE_USER_MAKE_RULES_OVERRIDE=/var/tmp/portage/sci-libs/flann-1.6.11/temp/gentoo_rules.cmake  /var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11-src
Not searching for unused variables given on the command line.
loading initial cache file /var/tmp/portage/sci-libs/flann-1.6.11/temp/gentoo_common_config.cmake
-- The C compiler identification is GNU
CMake Error at /usr/share/cmake/Modules/CMakeDetermineCXXCompiler.cmake:43 (MESSAGE):
  Could not find compiler set in environment variable CXX:

  mpicxx.

Call Stack (most recent call first):
  CMakeLists.txt:7 (project)


CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER_ENV_VAR
CMake Error: Error required internal CMake variable not set, cmake may be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER
CMake Error: Could not find cmake module file:/var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11_build/CMakeFiles/CMakeCXXCompiler.cmake
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!
 * ERROR: sci-libs/flann-1.6.11 failed (configure phase):
 *   cmake failed
 * 
 * Call stack:
 *     ebuild.sh, line   56:  Called src_configure
 *   environment, line 5416:  Called cmake-utils_src_configure
 *   environment, line 1391:  Called _execute_optionaly 'src_configure'
 *   environment, line  391:  Called enable_cmake-utils_src_configure
 *   environment, line 1702:  Called die
 * The specific snippet of code:
 *       "${CMAKE_BINARY}" "${cmakeargs[@]}" "${CMAKE_USE_DIR}" || die "cmake failed";
 * 
 * If you need support, post the output of 'emerge --info =sci-libs/flann-1.6.11',
 * the complete build log and the output of 'emerge -pqv =sci-libs/flann-1.6.11'.
 * The complete build log is located at '/var/tmp/portage/sci-libs/flann-1.6.11/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sci-libs/flann-1.6.11/temp/environment'.
 * S: '/var/tmp/portage/sci-libs/flann-1.6.11/work/flann-1.6.11-src'

>>> Failed to emerge sci-libs/flann-1.6.11, Log file:

>>>  '/var/tmp/portage/sci-libs/flann-1.6.11/temp/build.log'