g++ knows about C++98 selection flags since at least 3.4

https://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/C-Dialect-Options.html#C-Dialect-Options

Modules/Compiler/GNU-CXX.cmake

@@ -11,8 +11,7 @@ else()
   endif()
 endif()
 
-if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
-  # Supported since 4.3
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
   set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "-std=c++98")
   set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "-std=gnu++98")
 endif()