Reference gcc with unknown commit: 4e995bd73c4490edfe5080ec6014d63aa9abed5f

[wzssyqa]

https://github.com/rust-lang/gcc/tree/4e995bd73c4490edfe5080ec6014d63aa9abed5f
is not pushed into https://github.com/rust-lang/gcc/

We get a complain that: This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.