Use CMake install directories instead of hardcoded (#4481)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1537d83..0329147 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -239,15 +239,16 @@
 endif()
 
 if(FLATBUFFERS_INSTALL)
-  install(DIRECTORY include/flatbuffers DESTINATION include)
+  include(GNUInstallDirs)
+  install(DIRECTORY include/flatbuffers DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
   if(FLATBUFFERS_BUILD_FLATLIB)
-    install(TARGETS flatbuffers DESTINATION lib)
+    install(TARGETS flatbuffers DESTINATION ${CMAKE_INSTALL_LIBDIR})
   endif()
   if(FLATBUFFERS_BUILD_FLATC)
-    install(TARGETS flatc DESTINATION bin)
+    install(TARGETS flatc DESTINATION ${CMAKE_INSTALL_BINDIR})
   endif()
   if(FLATBUFFERS_BUILD_SHAREDLIB)
-    install(TARGETS flatbuffers_shared DESTINATION lib)
+    install(TARGETS flatbuffers_shared DESTINATION ${CMAKE_INSTALL_LIBDIR})
   endif()
 endif()