Some gcc hardening options were added, however since we add
"-Wl,--as-needed" we end up with "-Wl,--as-needed;-Wl,-z,relro" which
leads to linker errors about unknown options, if we make it so the
as-needed option is the last option on the line, everything is fine.

diff --git a/src/cpp/CMakeLists.txt b/src/cpp/CMakeLists.txt
index 0589ca0..fe5bd5f 100644
--- a/src/cpp/CMakeLists.txt
+++ b/src/cpp/CMakeLists.txt
@@ -57,7 +57,7 @@ if(UNIX)
       add_definitions(-D_FORTIFY_SOURCE=2)
       add_definitions(-fstack-protector --param ssp-buffer-size=4)
       add_definitions(-pie -fPIE)
-      set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-z,relro,-z,now")
+      set(CMAKE_EXE_LINKER_FLAGS "-Wl,-z,relro,-z,now ${CMAKE_EXE_LINKER_FLAGS}")
    endif()
 
 # Win32 specific global directives