This cannot be defined in v8config.h because target architecture
detection is not done in that file.
This CL moves the logic to set V8_HAS_PTHREAD_JIT_WRITE_PROTECT to
src/base/build_config.h, which also defines the V8_TARGET_ARCH* macros.

R=jkummerow@chromium.org, mlippautz@chromium.org

Bug: chromium:1238029
Change-Id: I2a688dad32b83df1d26bf23b15bf4485d78c8cc6
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3085271
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76198}