Fix cmakelists (#2716)

flags.cmake

@@ -2,7 +2,7 @@ option(SPINE_SANITIZE "Build with sanitization" OFF)
 option(SPINE_SET_COMPILER_FLAGS "Set compiler flags" ON)
 
 if (NOT SPINE_SET_COMPILER_FLAGS)
-    return();
+    return()
 endif()
 
 if(MSVC)