pass -Wl,-z,origin to set DF_ORIGIN when using rpath

 
DF_ORIGIN flag signifies that the object being loaded may make reference to the $ORIGIN substitution string.

Some implementations are just ignoring DF_ORIGIN and do substitution for $ORIGIN if present (whatever DF_ORIGIN presence or not) like glibc. But some others mandate the present of DF_ORIGIN for the substitution (like OpenBSD).
 
Set the flag inconditionally if rpath is wanted.

compiler/rustc_codegen_ssa/src/back/rpath.rs

@@ -34,6 +34,7 @@ pub fn get_rpath_flags(config: &mut RPathConfig<'_>) -> Vec<String> {
 fn rpaths_to_flags(rpaths: &[String]) -> Vec<String> {
     let mut ret = Vec::with_capacity(rpaths.len()); // the minimum needed capacity
 
+    ret.push(String::from("-Wl,-z,origin"));
     for rpath in rpaths {
         if rpath.contains(',') {
             ret.push("-Wl,-rpath".into());

src/bootstrap/builder.rs

@@ -1176,6 +1176,7 @@ impl<'a> Builder<'a> {
                 rustflags.arg("-Zosx-rpath-install-name");
                 Some("-Wl,-rpath,@loader_path/../lib")
             } else if !target.contains("windows") {
+                rustflags.arg("-Clink-args=-Wl,-z,origin");
                 Some("-Wl,-rpath,$ORIGIN/../lib")
             } else {
                 None