From 8fc058109bacdecdb6e2723d4371ab85670d43d2 Mon Sep 17 00:00:00 2001
From: David Wood <david.wood2@arm.com>
Date: Thu, 26 Mar 2026 14:59:13 +0000
Subject: [PATCH] bootstrap: `-Zjson-target-spec` for synthetic targets

---
 src/bootstrap/src/core/builder/cargo.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index 16065cbdae1fa..b4ef00bd4ea0d 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -122,6 +122,9 @@ impl Cargo {
         cmd_kind: Kind,
     ) -> Cargo {
         let mut cargo = builder.cargo(compiler, mode, source_type, target, cmd_kind);
+        if target.synthetic {
+            cargo.arg("-Zjson-target-spec");
+        }
 
         match cmd_kind {
             // No need to configure the target linker for these command types.
@@ -165,7 +168,11 @@ impl Cargo {
         target: TargetSelection,
         cmd_kind: Kind,
     ) -> Cargo {
-        builder.cargo(compiler, mode, source_type, target, cmd_kind)
+        let mut cargo = builder.cargo(compiler, mode, source_type, target, cmd_kind);
+        if target.synthetic {
+            cargo.arg("-Zjson-target-spec");
+        }
+        cargo
     }
 
     pub fn rustdocflag(&mut self, arg: &str) -> &mut Cargo {