Revert "rustc: Provide compiler-rt sources"
Revert "rustc: Provide compiler-rt sources"

This reverts commit b7a828031238b0962cd91131eba50844ef401b93. It's no
longer needed with Rust 1.38.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs