tests: Rename unix_sigpipe.rs to unix_sigpipe-bare.rs for clarity

The test is for the "bare" variant of the attribute that looks like this:

    #[unix_sigpipe]

which is not allowed, because it must look like this:

    #[unix_sigpipe = "sig_ign"]

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.rs b/tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.rs
new file mode 100644
index 00000000000..7bf1c7350c3
--- /dev/null
+++ b/tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.rs
@@ -0,0 +1,4 @@
+#![feature(unix_sigpipe)]
+
+#[unix_sigpipe] //~ error: valid values for `#[unix_sigpipe = "..."]` are `inherit`, `sig_ign`, or `sig_dfl`
+fn main() {}