Reorder compile options to have user-defined last

The previous version would put the user-defined options first. However,
the default options include e.g., -Wall. If a user tries to override
(see for instance the next commit) -Wall or other options might override
this and not honor the user choice.

To always have the user have the last work, put user-defined compile
options last.

CMakeLists.txt

@@ -175,9 +175,9 @@ if(CMAKE_C_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang
 endif()
 
 set(CMAKE_C_FLAGS
-  "${CMAKE_C_FLAGS} ${C_FLAGS_PROCESSOR} ${commonOpts} -std=gnu11 -funroll-loops")
+  "${C_FLAGS_PROCESSOR} ${commonOpts} -std=gnu11 -funroll-loops ${CMAKE_C_FLAGS}")
 set(CMAKE_CXX_FLAGS
-  "${CMAKE_CXX_FLAGS} ${C_FLAGS_PROCESSOR}  ${commonOpts} -std=c++11")
+  "${C_FLAGS_PROCESSOR}  ${commonOpts} -std=c++11 ${CMAKE_CXX_FLAGS}")
 
 
 add_boolean_option(SANITIZE_ADDRESS False "enable the address sanitizer (ASan)" ON)