Fix linking Mac Catalyst by including LC_BUILD_VERSION in object files

compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -188,6 +188,11 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
     };
 
     let mut file = write::Object::new(binary_format, architecture, endianness);
+    if sess.target.is_like_osx {
+        if let Some(build_version) = macho_object_build_version_for_target(&sess.target) {
+            file.set_macho_build_version(build_version)
+        }
+    }
     let e_flags = match architecture {
         Architecture::Mips => {
             let arch = match sess.target.options.cpu.as_ref() {
@@ -258,6 +263,33 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
     Some(file)
 }
 
+/// Apple's LD, when linking for Mac Catalyst, requires object files to
+/// contain information about what they were built for (LC_BUILD_VERSION):
+/// the platform (macOS/watchOS etc), minimum OS version, and SDK version.
+/// This returns a `MachOBuildVersion` if necessary for the target.
+fn macho_object_build_version_for_target(
+    target: &Target,
+) -> Option<object::write::MachOBuildVersion> {
+    if !target.llvm_target.ends_with("-macabi") {
+        return None;
+    }
+    /// The `object` crate demands "X.Y.Z encoded in nibbles as xxxx.yy.zz"
+    /// e.g. minOS 14.0 = 0x000E0000, or SDK 16.2 = 0x00100200
+    fn pack_version((major, minor): (u32, u32)) -> u32 {
+        (major << 16) | (minor << 8)
+    }
+
+    let platform = object::macho::PLATFORM_MACCATALYST;
+    let min_os = (14, 0);
+    let sdk = (16, 2);
+
+    let mut build_version = object::write::MachOBuildVersion::default();
+    build_version.platform = platform;
+    build_version.minos = pack_version(min_os);
+    build_version.sdk = pack_version(sdk);
+    Some(build_version)
+}
+
 pub enum MetadataPosition {
     First,
     Last,

compiler/rustc_target/src/spec/aarch64_apple_ios_macabi.rs

@@ -2,7 +2,7 @@ use super::apple_base::{opts, Arch};
 use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, Target, TargetOptions};
 
 pub fn target() -> Target {
-    let llvm_target = "arm64-apple-ios-macabi";
+    let llvm_target = "arm64-apple-ios14.0-macabi";
 
     let arch = Arch::Arm64_macabi;
     let mut base = opts("ios", arch);

compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs

@@ -2,7 +2,7 @@ use super::apple_base::{opts, Arch};
 use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, TargetOptions};
 
 pub fn target() -> Target {
-    let llvm_target = "x86_64-apple-ios-macabi";
+    let llvm_target = "x86_64-apple-ios14.0-macabi";
 
     let arch = Arch::X86_64_macabi;
     let mut base = opts("ios", arch);