restore: sa_restorer not present in mips* architectures

Issue: #38

build.rs

@@ -58,7 +58,18 @@ fn check_sa_restorer(target_arch: &str) {
     //println!("cargo::rustc-check-cfg=cfg(nc_has_sa_restorer)");
     println!("cargo:rustc-check-cfg=cfg(nc_has_sa_restorer)");
 
-    if target_arch != "riscv64" {
+    // Some architectures do not contain sa_restorer property in sa_sigaction_t.
+    // - mips
+    // - mipsel
+    // - mips64
+    // - mips64el
+    // - riscv64
+    if target_arch != "mips"
+        && target_arch != "mipsel"
+        && target_arch != "mips64"
+        && target_arch != "mips64el"
+        && target_arch != "riscv64"
+    {
         println!("cargo:rustc-cfg=nc_has_sa_restorer");
     }
 }

src/restore/c.rs

@@ -2,11 +2,13 @@
 // Use of this source is governed by Apache-2.0 License that can be found
 // in the LICENSE file.
 
+#[cfg(nc_has_sa_restorer)]
 use crate::{restorefn_t, rt_sigaction, sigaction_t, SIGSEGV};
 
 /// Reuse sa restorer function.
 ///
 /// This method is unreliable.
+#[cfg(nc_has_sa_restorer)]
 #[must_use]
 #[inline]
 pub fn get_sa_restorer() -> Option<restorefn_t> {
@@ -18,3 +20,10 @@ pub fn get_sa_restorer() -> Option<restorefn_t> {
         None
     }
 }
+
+#[cfg(not(nc_has_sa_restorer))]
+#[must_use]
+#[inline]
+pub fn get_sa_restorer() -> Option<crate::restorefn_t> {
+    None
+}