Ignore needless_raw_string_hashes clippy lint

    warning: unnecessary hashes around raw string literal
      --> build.rs:17:21
       |
    17 |   const PROBE: &str = r#"
       |  _____________________^
    18 | |     #![feature(error_generic_member_access)]
    19 | |
    20 | |     use std::backtrace::Backtrace;
    ...  |
    45 | |     const _: fn(&dyn Error) -> Option<&Backtrace> = |err| error::request_ref::<Backtrace>(err);
    46 | | "#;
       | |__^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_raw_string_hashes
       = note: `-W clippy::needless-raw-string-hashes` implied by `-W clippy::all`
       = help: to override `-W clippy::all` add `#[allow(clippy::needless_raw_string_hashes)]`
    help: remove all the hashes around the literal
       |
    17 ~ const PROBE: &str = r"
    18 |     #![feature(error_generic_member_access)]
     ...
    45 |     const _: fn(&dyn Error) -> Option<&Backtrace> = |err| error::request_ref::<Backtrace>(err);
    46 ~ ";
       |

build.rs

@@ -1,4 +1,4 @@
-#![allow(clippy::option_if_let_else)]
+#![allow(clippy::needless_raw_string_hashes, clippy::option_if_let_else)]
 
 use std::env;
 use std::fs;