Allows to disable direct TLS segment access (%fs or %gs). GCC supports a similar flag, it can be useful in some circumstances, e.g. when a thread context block needs to be updated directly from user space. More info and specific use cases: https://bugs.llvm.org/show_bug.cgi?id=16145
There is another revision for LLVM as well.
Related: D53103
This file is automatically generated based on the options .td files, so no need to update it here.