Merge pull request #5516 from KeithMoyer/master

Clean up unnecessary compile warning with GCC

BUILD

@@ -54,7 +54,6 @@ COPTS = select({
         "-Wno-sign-compare",
         "-Wno-unused-function",
         # Prevents ISO C++ const string assignment warnings for pyext sources.
-        "-Wno-writable-strings",
         "-Wno-write-strings",
     ],
 })