FIx codegen backend compilation

Author: bjorn3

Cargo.lock

@@ -1845,9 +1845,9 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mach"
-version = "0.2.3"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "86dd2487cdfea56def77b88438a2c915fb45113c5319bfe7e14306ca4cd0b0e1"
+checksum = "b823e83b2affd8f40a9ee8c29dbc56404c1e34cd2710921f2801e2cf29527afa"
 dependencies = [
  "libc",
 ]
@@ -2838,9 +2838,9 @@ checksum = "7fe5bd57d1d7414c6b5ed48563a2c855d995ff777729dcd91c369ec7fea395ae"
 
 [[package]]
 name = "region"
-version = "2.1.2"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "448e868c6e4cfddfa49b6a72c95906c04e8547465e9536575b95c70a4044f856"
+checksum = "877e54ea2adcd70d80e9179344c97f93ef0dffd6b03e1f4529e6e83ab2fa9ae0"
 dependencies = [
  "bitflags",
  "libc",

src/bootstrap/builder.rs

@@ -924,6 +924,8 @@ impl<'a> Builder<'a> {
             // problem, somehow -- not really clear why -- but we know that this
             // fixes things.
             Mode::ToolRustc => metadata.push_str("tool-rustc"),
+            // Same for codegen backends.
+            Mode::Codegen => metadata.push_str("codegen"),
             _ => {}
         }
         cargo.env("__CARGO_DEFAULT_LIB_METADATA", &metadata);