Constant rustc_session::config::sigpipe::DEFAULT

pub const DEFAULT: u8 = 0;

The default value if -Zon-broken-pipe=... is not specified. This resolves to SIG_IGN in library/std/src/sys/pal/unix/mod.rs.

Note that SIG_IGN has been the Rust default since 2014. See https://github.com/rust-lang/rust/issues/62569.