Link to execinfo on NetBSD

Author: Kobzol

compiler/rustc_llvm/build.rs

@@ -251,8 +251,11 @@ fn main() {
     } else if target.contains("windows-gnu") {
         println!("cargo:rustc-link-lib=shell32");
         println!("cargo:rustc-link-lib=uuid");
-    } else if target.contains("netbsd") || target.contains("haiku") || target.contains("darwin") {
+    } else if target.contains("haiku") || target.contains("darwin") {
         println!("cargo:rustc-link-lib=z");
+    } else if target.contains("netbsd") {
+        println!("cargo:rustc-link-lib=z");
+        println!("cargo:rustc-link-lib=execinfo");
     }
     cmd.args(&components);