diff --git a/compiler-builtins/build.rs b/compiler-builtins/build.rs
index e86c784b5..093fa11a0 100644
--- a/compiler-builtins/build.rs
+++ b/compiler-builtins/build.rs
@@ -538,7 +538,22 @@ mod c {
         // Support deterministic builds by remapping the __FILE__ prefix if the
         // compiler supports it.  This fixes the nondeterminism caused by the
         // use of that macro in lib/builtins/int_util.h in compiler-rt.
-        build.flag_if_supported(&format!("-ffile-prefix-map={}=.", root.display()));
+
+        // `RUSTC_DEBUGINFO_MAP` is a bootstrap-specific env var (not a general
+        // Cargo/rustc mechanism) containing the `--remap-path-prefix` mappings
+        // bootstrap passes to rustc via its rustc shim. Bootstrap uses this
+        // instead of RUSTFLAGS because Cargo doesn't always forward RUSTFLAGS to
+        // build scripts and proc-macros (rust-lang/cargo#4423).
+        //
+        // Apply each mapping via -ffile-prefix-map, mirroring rustc_llvm's
+        // build.rs for the same env var.
+        if let Some(maps) = env::var_os("RUSTC_DEBUGINFO_MAP")
+            && let Some(maps_str) = maps.to_str()
+        {
+            for map in maps_str.split('\t') {
+                build.flag_if_supported(&format!("-ffile-prefix-map={map}"));
+            }
+        }
 
         // Include out-of-line atomics for aarch64, which are all generated by supplying different
         // sets of flags to the same source file.