Rollup merge of #136892 - erickt:fuchsia-target, r=jieyouxu

Sync Fuchsia target spec with clang Fuchsia driver

This updates the Fuchsia target spec with the [Clang Fuchsia driver], which picks up a few changes:

* Adds `-z start-stop-visibility=hidden` and `-z rel` to the pre link arguments.
* Adds `--execute-only` and `--fix-cortex-a53-843419` for `aarch64-unknown-fuchsia`.
* Enables the equivalent cpu features for `x86-64-v2` for `x86_64-unknown-fuchsia`, which is our minimum supported x86_64 platform according to [RFC-0073].

try-job: x86_64-fuchsia

[Clang Fuchsia driver]: https://github.com/llvm/llvm-project/blob/8374d421861cd3d47e21ae7889ba0b4c498e8d85/clang/lib/Driver/ToolChains/Fuchsia.cpp
[RFC-0073]: https://fuchsia.dev/fuchsia-src/contribute/governance/rfcs/0073_x86_64_platform_requirement

Author: jhpratt