Re-enable incremental compilation for the sysroot

rust-lang/rust#74946 for fixed

Author: bjorn3

build_system/build_sysroot.rs

@@ -193,8 +193,6 @@ fn build_clif_sysroot_for_triple(
         "RUSTC",
         env::current_dir().unwrap().join(target_dir).join("bin").join("cg_clif_build_sysroot"),
     );
-    // FIXME Enable incremental again once rust-lang/rust#74946 is fixed
-    build_cmd.env("CARGO_INCREMENTAL", "0").env("__CARGO_DEFAULT_LIB_METADATA", "cg_clif");
     spawn_and_wait(build_cmd);
 
     // Copy all relevant files to the sysroot