[base] Set MAP_JIT when allocating V8 pages on Fuchsia

The V8 JIT requires the ability to re-map heap pages as executable,
but Fuchsia only allows this with pages allocated with MAP_JIT.

Bug: 927411
Change-Id: I589981de14e0a8646ed3e245d237f10b92b26118
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504507
Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Matthew Dempsky <mdempsky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638413}
1 file changed