Ignore system config (for Gentoo)

Author: 0181532686cf4a31163be0bf3e6bb6732bf

cmake/BoostLibInstaller.cmake

@@ -180,7 +180,7 @@ function(boost_lib_installer req_boost_version req_boost_libs)
     # b2 headers
     if(NOT EXISTS ${install_dir}/boost/)
         message(STATUS "Generating headers ...")
-        execute_process(COMMAND ${b2_command} headers WORKING_DIRECTORY ${install_dir} RESULT_VARIABLE err OUTPUT_VARIABLE err_msg)
+        execute_process(COMMAND ${b2_command} --ignore-site-config headers WORKING_DIRECTORY ${install_dir} RESULT_VARIABLE err OUTPUT_VARIABLE err_msg)
         if(err)
             message(FATAL_ERROR "b2 error:\n${err_msg}")
         endif(err)

cmake/GetBoostLibB2Args.cmake

@@ -18,7 +18,8 @@ function(get_boots_lib_b2_args)
                stage
                --stagedir=${stage_dir}
                -d+2
-               --hash)
+               --hash
+               --ignore-site-config)
 
     message(STATUS "Generating b2 args.")