make OpenBSD to use libc++ instead of (e)stdc++

src/librustc_llvm/build.rs

@@ -252,8 +252,8 @@ fn main() {
     let llvm_static_stdcpp = env::var_os("LLVM_STATIC_STDCPP");
 
     let stdcppname = if target.contains("openbsd") {
-        // OpenBSD has a particular C++ runtime library name
-        "estdc++"
+        // llvm-config on OpenBSD doesn't mention stdlib=libc++
+        "c++"
     } else if target.contains("netbsd") && llvm_static_stdcpp.is_some() {
         // NetBSD uses a separate library when relocation is required
         "stdc++_pic"