add fixme

Author: jyn514

src/bootstrap/src/core/builder.rs

@@ -1155,6 +1155,7 @@ impl<'a> Builder<'a> {
     pub fn cargo_clippy_cmd(&self, run_compiler: Compiler) -> Command {
         let initial_sysroot_bin = self.initial_rustc.parent().unwrap();
         // Set PATH to include the sysroot bin dir so clippy can find cargo.
+        // FIXME: once rust-clippy#11944 lands on beta, set `CARGO` directly instead.
         let path = t!(env::join_paths(
             // The sysroot comes first in PATH to avoid using rustup's cargo.
             std::iter::once(PathBuf::from(initial_sysroot_bin))