CMakeLists.txt: Update FastLinuxReleaseBuildMode to alter CMAKE_CXX_FLAGS_RELWITHDEBINFO instead of CMAKE_CXX_FLAGS_RELEASE

Author: NeilJustice

CMakeLists.txt

@@ -18,7 +18,7 @@ if(UNIX)
       message("FastLinuxDebugBuildMode enabled: -g removed")
    endif()
    if(FastLinuxReleaseBuildMode)
-      replace(CMAKE_CXX_FLAGS_RELEASE "-O2" "")
+      replace(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2" "")
       message("FastLinuxReleaseBuildMode enabled: -O2 removed")
    endif()
    if(ClangTidyMode)