Support `#[unix_sigpipe = "inherit|sig_dfl|sig_ign"]` on `fn main()`

This makes it possible to instruct libstd to never touch the signal
handler for `SIGPIPE`, which makes programs pipeable by default (e.g.
with `./your-program | head -n 1`) without `ErrorKind::BrokenPipe`
errors.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/test/ui/attributes/unix_sigpipe/unix_sigpipe-wrong.rs b/src/test/ui/attributes/unix_sigpipe/unix_sigpipe-wrong.rs
new file mode 100644
index 00000000000..4ec25de00ec
--- /dev/null
+++ b/src/test/ui/attributes/unix_sigpipe/unix_sigpipe-wrong.rs
@@ -0,0 +1,4 @@
+#![feature(unix_sigpipe)]
+
+#[unix_sigpipe = "wrong"] //~ error: valid values for `#[unix_sigpipe = "..."]` are `inherit`, `sig_ign`, or `sig_dfl`
+fn main() {}