Add EIGENPY_SITELIB_ROOT to customize sitelib install location.

python/CMakeLists.txt

@@ -29,7 +29,11 @@ TARGET_LINK_BOOST_PYTHON(${PYWRAP})
 #IF(BUILD_WITH_COMMIT_VERSION)
 #  TAG_LIBRARY_VERSION(${PYWRAP})
 #ENDIF(BUILD_WITH_COMMIT_VERSION)
-SET(${PYWRAP}_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/${PYTHON_SITELIB})
+IF(DEFINED EIGENPY_SITELIB_ROOT AND EIGENPY_SITELIB_ROOT)
+  SET(${PYWRAP}_INSTALL_DIR ${EIGENPY_SITELIB_ROOT}/${PYTHON_SITELIB})
+ELSE()
+  SET(${PYWRAP}_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/${PYTHON_SITELIB})
+ENDIF()
 
 SET_PROPERTY(TARGET ${PYWRAP} PROPERTY LINKER_LANGUAGE CXX)
 IF(APPLE)