Using `thread_local` on AIX causes the following error during linking:
```
ld: 0711-317 ERROR: Undefined symbol: TLS init function for ...
```
To avoid the issue we can use the __thread keyword.

More on this gcc bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100641

Bug: v8:11755
Change-Id: Ic9738e8dfb7110b550328c5d9929f4453e545b0b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2903586Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#74642}