Auto merge of #63744 - Centril:rollup-g4l3ra9, r=Centril

Rollup of 7 pull requests

Successful merges:

 - #63216 (avoid unnecessary reservations in std::io::Take::read_to_end)
 - #63265 (Implement `nth_back` for ChunksExactMut)
 - #63691 (Fix bug in iter::Chain::size_hint)
 - #63722 (Don't use stage naming in RUSTFLAGS environment variables)
 - #63723 (Consolidate sigemptyset workarounds)
 - #63736 (Restore the rustc_plugin crate in the sysroot)
 - #63743 (Allow git to merge `Cargo.lock`)

Failed merges:

r? @ghost

1 files changed, 5 insertions, 5 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index f0054c36c0c..afde076a35a 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -859,12 +859,12 @@ impl<'a> Builder<'a> {
             stage = compiler.stage;
         }
 
-        let mut extra_args = env::var(&format!("RUSTFLAGS_STAGE_{}", stage)).unwrap_or_default();
+        let mut extra_args = String::new();
         if stage != 0 {
-            let s = env::var("RUSTFLAGS_STAGE_NOT_0").unwrap_or_default();
-            if !extra_args.is_empty() {
-                extra_args.push_str(" ");
-            }
+            let s = env::var("RUSTFLAGS_NOT_BOOTSTRAP").unwrap_or_default();
+            extra_args.push_str(&s);
+        } else {
+            let s = env::var("RUSTFLAGS_BOOTSTRAP").unwrap_or_default();
             extra_args.push_str(&s);
         }