Added a little safeguard against GCC optimizer bug to CMakeLists.txt.

7 jobs for gcc_optimizer_bug in 20 minutes and 39 seconds
Status Name Job ID Coverage
  Test
passed clang-c++11 #10013
Linux

00:20:38

passed clang-c++98 #10015
Linux

00:17:54

passed cppcheck #10018
Linux

00:00:26

passed gcc-c++11 #10012
Linux

00:04:20

passed gcc-c++98 #10014
Linux

00:03:57

passed macos-c++11 #10016
Apple

00:16:23

passed macos-c++98 #10017
Apple

00:15:20