Some platform updates.

[ehuss]

• aarch64-apple-darwin: Add the aarch64-apple-darwin target  rust#74541
• thumbv4t-none-eabi: Add a thumbv4t-none-eabi target rust#74419
• RISC-V GNU/Linux RISC-V GNU/Linux as host platform rust#72973 (no change?)
  • Note: I think there is some ambiguity in the table. A check-mark for rustc can mean "it compiles" and also mean "automated builds with rustup artifacts".
• x86_64-unknown-illumos: build dist for x86_64-unknown-illumos rust#71272

[ehuss]

What do people think about possibly moving this table to the rustc book in the rust-lang/rust repository? It would then be possible to do some automated checks or generation, to ensure it is somewhat up-to-date. It would also be easier to ask people who are adding/changing support to update the list in the same PR that makes the change.

[Mark-Simulacrum]

I think that's a good idea! Checking I imagine is going to be "Hard" but maybe there's some strategy we can come up with that would ease that.

[tesuji]

The page still needs to be exist to point to new URL. Otherwise many links will break.

[XAMPPRocky]

Thank you for your PR! @ehuss Would you be able to create a separate issue for improving the platform support table? I'm going to merge this and I wouldn't want that to get lost.