Rollup merge of #131016 - madsmtm:no-sdk-version-in-object, r=jieyouxu

Apple: Do not specify an SDK version in `rlib` object files

This was added in https://github.com/rust-lang/rust/pull/114114, but is unnecessary, since it ends up being overwritten when linking anyhow, and it feels wrong to embed some arbitrary SDK version in here. The object files produced by LLVM also do not set this, and the tooling shows `n/a` when it's `0`, so it seems to genuinely be optional in object files.

I've also added a test for the different places the SDK version shows up, and documented a bit more in the code how SDK versions work.

See https://github.com/rust-lang/rust/issues/129432 for the bigger picture.

Tested with (excludes the same few targets as in https://github.com/rust-lang/rust/pull/130435):
```console
./x test tests/run-make/apple-sdk-version --target aarch64-apple-darwin,aarch64-apple-ios,aarch64-apple-ios-macabi,aarch64-apple-ios-sim,aarch64-apple-tvos,aarch64-apple-tvos-sim,aarch64-apple-visionos,aarch64-apple-visionos-sim,aarch64-apple-watchos,aarch64-apple-watchos-sim,arm64_32-apple-watchos,armv7k-apple-watchos,armv7s-apple-ios,x86_64-apple-darwin,x86_64-apple-ios,x86_64-apple-ios-macabi,x86_64-apple-tvos,x86_64-apple-watchos-sim,x86_64h-apple-darwin
IPHONEOS_DEPLOYMENT_TARGET=10.0 ./x test tests/run-make/apple-sdk-version --target=i386-apple-ios
```

CC `@BlackHoleFox,` you [originally commented on these values](https://github.com/rust-lang/rust/pull/114114#discussion_r1300599445).

`@rustbot` label O-apple

2 files changed, 1 insertions, 18 deletions

diff --git a/compiler/rustc_target/src/spec/base/apple/mod.rs b/compiler/rustc_target/src/spec/base/apple/mod.rs
index 81b5a936d35..73763cf034c 100644
--- a/compiler/rustc_target/src/spec/base/apple/mod.rs
+++ b/compiler/rustc_target/src/spec/base/apple/mod.rs
@@ -158,23 +158,6 @@ pub(crate) fn base(
     (opts, llvm_target(os, arch, abi), arch.target_arch())
 }
 
-pub fn sdk_version(platform: u32) -> Option<(u16, u8)> {
-    // NOTE: These values are from an arbitrary point in time but shouldn't make it into the final
-    // binary since the final link command will have the current SDK version passed to it.
-    match platform {
-        object::macho::PLATFORM_MACOS => Some((13, 1)),
-        object::macho::PLATFORM_IOS
-        | object::macho::PLATFORM_IOSSIMULATOR
-        | object::macho::PLATFORM_TVOS
-        | object::macho::PLATFORM_TVOSSIMULATOR
-        | object::macho::PLATFORM_MACCATALYST => Some((16, 2)),
-        object::macho::PLATFORM_WATCHOS | object::macho::PLATFORM_WATCHOSSIMULATOR => Some((9, 1)),
-        // FIXME: Upgrade to `object-rs` 0.33+ implementation with visionOS platform definition
-        11 | 12 => Some((1, 0)),
-        _ => None,
-    }
-}
-
 pub fn platform(target: &Target) -> Option<u32> {
     Some(match (&*target.os, &*target.abi) {
         ("macos", _) => object::macho::PLATFORM_MACOS,
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index d1fcfe4adef..c557091242e 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -61,7 +61,7 @@ pub mod crt_objects;
 mod base;
 pub use base::apple::{
     deployment_target_for_target as current_apple_deployment_target,
-    platform as current_apple_platform, sdk_version as current_apple_sdk_version,
+    platform as current_apple_platform,
 };
 pub use base::avr_gnu::ef_avr_arch;