Rollup merge of #77202 - ehuss:defer-apple-sdkroot, r=petrochenkov

Defer Apple SDKROOT detection to link time.

This defers the detection of the SDKROOT for Apple iOS/tvOS targets to link time, instead of when the `Target` is defined. This allows commands that don't need to link to work (like `rustdoc` or `rustc --print=target-list`). This also makes `--print=target-list` a bit faster.

This also removes the note in the platform support documentation about these targets being missing. When I wrote it, I misunderstood how the SDKROOT stuff worked.

Notes:
* This means that JSON spec targets can't explicitly override these flags. I think that is probably fine, as I believe the value is generally required, and can be set with the SDKROOT environment variable.
* This changes `x86_64-apple-tvos` to use `appletvsimulator`. I think the original code was wrong (it was using `iphonesimulator`). Also, `x86_64-apple-tvos` seems broken in general, and I cannot build it locally. The `data_layout` does not appear to be correct (it is a copy of the arm64 layout instead of the x86_64 layout). I have not tried building Apple's LLVM to see if that helps, but I suspect it is just wrong (I'm uncertain since I don't know how the tvOS simulator works with its bitcode-only requirements).
* I'm tempted to remove the use of `Result` for built-in target definitions, since I don't think they should be fallible. This was added in https://github.com/rust-lang/rust/pull/34980, but that only relates to JSON definitions. I think the built-in targets shouldn't fail. I can do this now, or not.

Fixes #36156
Fixes #76584

2 files changed, 8 insertions, 11 deletions

diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index 9b2474a95df..6c605f045e5 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -57,7 +57,7 @@ Specifically, these platforms are required to have each of the following:
 
 target | std | host | notes
 -------|-----|------|-------
-`aarch64-apple-ios` | ✓[^apple] |  | ARM64 iOS
+`aarch64-apple-ios` | ✓ |  | ARM64 iOS
 `aarch64-fuchsia` | ✓ |  | ARM64 Fuchsia
 `aarch64-linux-android` | ✓ |  | ARM64 Android
 `aarch64-pc-windows-msvc` | ✓ |  | ARM64 Windows MSVC
@@ -122,7 +122,7 @@ target | std | host | notes
 `wasm32-unknown-emscripten` | ✓ |  | WebAssembly via Emscripten
 `wasm32-unknown-unknown` | ✓ |  | WebAssembly
 `wasm32-wasi` | ✓ |  | WebAssembly with WASI
-`x86_64-apple-ios` | ✓[^apple] |  | 64-bit x86 iOS
+`x86_64-apple-ios` | ✓ |  | 64-bit x86 iOS
 `x86_64-fortanix-unknown-sgx` | ✓ |  | [Fortanix ABI] for 64-bit Intel SGX
 `x86_64-fuchsia` | ✓ |  | 64-bit Fuchsia
 `x86_64-linux-android` | ✓ |  | 64-bit x86 Android
@@ -146,7 +146,7 @@ not available.
 target | std | host | notes
 -------|-----|------|-------
 `aarch64-apple-darwin` | ? |  | ARM64 macOS
-`aarch64-apple-tvos` | *[^apple] |  | ARM64 tvOS
+`aarch64-apple-tvos` | * |  | ARM64 tvOS
 `aarch64-unknown-cloudabi` | ✓ |  | ARM64 CloudABI
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 `aarch64-unknown-hermit` | ? |  |
@@ -158,16 +158,16 @@ target | std | host | notes
 `armv4t-unknown-linux-gnueabi` | ? |  |
 `armv6-unknown-freebsd` | ✓ | ✓ | ARMv6 FreeBSD
 `armv6-unknown-netbsd-eabihf` | ? |  |
-`armv7-apple-ios` | ✓[^apple] |  | ARMv7 iOS, Cortex-a8
+`armv7-apple-ios` | ✓ |  | ARMv7 iOS, Cortex-a8
 `armv7-unknown-cloudabi-eabihf` | ✓ |  | ARMv7 CloudABI, hardfloat
 `armv7-unknown-freebsd` | ✓ | ✓ | ARMv7 FreeBSD
 `armv7-unknown-netbsd-eabihf` | ? |  |
 `armv7-wrs-vxworks-eabihf` | ? |  |
 `armv7a-none-eabihf` | * | | ARM Cortex-A, hardfloat
-`armv7s-apple-ios` | ✓[^apple] |  |
+`armv7s-apple-ios` | ✓ |  |
 `avr-unknown-gnu-atmega328` | ✗ |  | AVR. Requires `-Z build-std=core`
 `hexagon-unknown-linux-musl` | ? |  |
-`i386-apple-ios` | ✓[^apple] |  | 32-bit x86 iOS
+`i386-apple-ios` | ✓ |  | 32-bit x86 iOS
 `i686-apple-darwin` | ✓ | ✓ | 32-bit OSX (10.7+, Lion+)
 `i686-pc-windows-msvc` | ✓ |  | 32-bit Windows XP support
 `i686-unknown-cloudabi` | ✓ |  | 32-bit CloudABI
@@ -203,8 +203,8 @@ target | std | host | notes
 `thumbv7a-uwp-windows-msvc` | ✓ |  |
 `thumbv7neon-unknown-linux-musleabihf` | ? |  | Thumb2-mode ARMv7a Linux with NEON, MUSL
 `thumbv4t-none-eabi` | * |  | ARMv4T T32
-`x86_64-apple-ios-macabi` | ✓[^apple] |  | Apple Catalyst
-`x86_64-apple-tvos` | *[^apple] | | x86 64-bit tvOS
+`x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst
+`x86_64-apple-tvos` | * | | x86 64-bit tvOS
 `x86_64-linux-kernel` | * |  | Linux kernel modules
 `x86_64-pc-solaris` | ? |  |
 `x86_64-pc-windows-msvc` | ✓ |  | 64-bit Windows XP support
@@ -221,4 +221,3 @@ target | std | host | notes
 `x86_64-wrs-vxworks` | ? |  |
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets
-[^apple]: These targets are only available on macOS.
diff --git a/src/tools/tier-check/src/main.rs b/src/tools/tier-check/src/main.rs
index b8d60a5e2fe..6a492bbff4d 100644
--- a/src/tools/tier-check/src/main.rs
+++ b/src/tools/tier-check/src/main.rs
@@ -25,8 +25,6 @@ fn main() {
     let doc_targets: HashSet<_> = doc_targets_md
         .lines()
         .filter(|line| line.starts_with('`') && line.contains('|'))
-        // These platforms only exist on macos.
-        .filter(|line| !line.contains("[^apple]") || cfg!(target_os = "macos"))
         .map(|line| line.split('`').skip(1).next().expect("expected target code span"))
         .collect();