Rollup merge of #120640 - Ayush1325:uefi-doc, r=Nilstrieb

Mark UEFI std support as WIP

Currently stdio and alloc support is present with open PRs for some of the other portions.

A prototype of almost all of std support can be found [here](https://github.com/tianocore/rust/tree/uefi-master). I will be up-streaming as much stuff as possible from there.

src/doc/rustc/src/platform-support.md

@@ -118,6 +118,7 @@ The `std` column in the table below has the following meanings:
 
 * ✓ indicates the full standard library is available.
 * \* indicates the target only supports [`no_std`] development.
+* ? indicates the standard library support is unknown or a work-in-progress.
 
 [`no_std`]: https://rust-embedded.github.io/book/intro/no-std.html
 
@@ -140,7 +141,7 @@ target | std | notes
 [`aarch64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ | ARM64 OpenHarmony
 `aarch64-unknown-none-softfloat` | * | Bare ARM64, softfloat
 `aarch64-unknown-none` | * | Bare ARM64, hardfloat
-[`aarch64-unknown-uefi`](platform-support/unknown-uefi.md) | * | ARM64 UEFI
+[`aarch64-unknown-uefi`](platform-support/unknown-uefi.md) | ? | ARM64 UEFI
 [`arm-linux-androideabi`](platform-support/android.md) | ✓ | ARMv6 Android
 `arm-unknown-linux-musleabi` | ✓ | ARMv6 Linux with musl 1.2.3
 `arm-unknown-linux-musleabihf` | ✓ | ARMv6 Linux with musl 1.2.3, hardfloat
@@ -162,7 +163,7 @@ target | std | notes
 [`i686-linux-android`](platform-support/android.md) | ✓ | 32-bit x86 Android [^x86_32-floats-return-ABI]
 `i686-unknown-freebsd` | ✓ | 32-bit FreeBSD [^x86_32-floats-return-ABI]
 `i686-unknown-linux-musl` | ✓ | 32-bit Linux with musl 1.2.3 [^x86_32-floats-return-ABI]
-[`i686-unknown-uefi`](platform-support/unknown-uefi.md) | * | 32-bit UEFI
+[`i686-unknown-uefi`](platform-support/unknown-uefi.md) | ? | 32-bit UEFI
 [`loongarch64-unknown-none`](platform-support/loongarch-none.md) | * |  | LoongArch64 Bare-metal (LP64D ABI)
 [`loongarch64-unknown-none-softfloat`](platform-support/loongarch-none.md) | * |  | LoongArch64 Bare-metal (LP64S ABI)
 [`nvptx64-nvidia-cuda`](platform-support/nvptx64-nvidia-cuda.md) | * | --emit=asm generates PTX code that [runs on NVIDIA GPUs]
@@ -199,7 +200,7 @@ target | std | notes
 [`x86_64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ | x86_64 OpenHarmony
 [`x86_64-unknown-none`](platform-support/x86_64-unknown-none.md) | * | Freestanding/bare-metal x86_64, softfloat
 `x86_64-unknown-redox` | ✓ | Redox OS
-[`x86_64-unknown-uefi`](platform-support/unknown-uefi.md) | * | 64-bit UEFI
+[`x86_64-unknown-uefi`](platform-support/unknown-uefi.md) | ? | 64-bit UEFI
 
 [^x86_32-floats-x87]: Floating-point support on `i586` targets is non-compliant: the `x87` registers and instructions used for these targets do not provide IEEE-754-compliant behavior, in particular when it comes to rounding and NaN payload bits. See [issue #114479][x86-32-float-issue].
 [wasi-rename]: https://github.com/rust-lang/compiler-team/issues/607