Remove line break of CMakeLists.txt (#4691)

Fix #4650
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 16a70b8..4d0ad47 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -126,8 +126,7 @@
         "${CMAKE_CXX_FLAGS} -faligned-new")
     endif()
     set(CMAKE_CXX_FLAGS
-      "${CMAKE_CXX_FLAGS} -Wunused-result -Werror=unused-result \
-                          -Wunused-parameter -Werror=unused-parameter")
+      "${CMAKE_CXX_FLAGS} -Wunused-result -Werror=unused-result -Wunused-parameter -Werror=unused-parameter")
   endif()
 
   # Certain platforms such as ARM do not use signed chars by default