Don't pass --system-libs to old llvm-config

src/SConscript

@@ -110,7 +110,8 @@ testenv.ParseConfig('pkg-config --cflags --libs glib-2.0')
 testenv_llvm_config_version = subprocess.Popen('%s --version' % env["LLVM_CONFIG"], \
                                                shell=True, \
                                                stdin=subprocess.PIPE, stdout=subprocess.PIPE).communicate()
-if LooseVersion(testenv_llvm_config_version[0]) < LooseVersion("3.9"):
+if LooseVersion(testenv_llvm_config_version[0]) < LooseVersion("3.9") and \
+   LooseVersion(testenv_llvm_config_version[0]) >= LooseVersion("3.5"):
     testenv_llvm_system_libs_flag = "--system-libs"
 else:
     testenv_llvm_system_libs_flag = ""