Auto merge of #3469 - devnexen:obsd_reg_riscv64, r=JohnTitor

openbsd riscv64 adding sigcontext

src/unix/bsd/netbsdlike/openbsd/riscv64.rs

@@ -1,6 +1,25 @@
 pub type c_long = i64;
 pub type c_ulong = u64;
 pub type c_char = u8;
+pub type ucontext_t = sigcontext;
+
+s! {
+    pub struct sigcontext {
+        __sc_unused: ::c_int,
+        pub sc_mask: ::c_int,
+        pub sc_ra: ::c_long,
+        pub sc_sp: ::c_long,
+        pub sc_gp: ::c_long,
+        pub sc_tp: ::c_long,
+        pub sc_t: [::c_long; 7],
+        pub sc_s: [::c_long; 12],
+        pub sc_a: [::c_long; 8],
+        pub sc_sepc: ::c_long,
+        pub sc_f: [::c_long; 32],
+        pub sc_fcsr: ::c_long,
+        pub sc_cookie: ::c_long,
+    }
+}
 
 // should be pub(crate), but that requires Rust 1.18.0
 cfg_if! {