linker: Add RPaths after LDFLAGS_BEFORE

Otherwise, the calling environment has no way to override RPaths set
automatically to in the linker stage. This is needed to allow program
install RPaths to superscede the detected dependency ones.

src/linker.cpp

@@ -28,14 +28,23 @@ constexpr bool remove_dynamic_linker = false;
 constexpr nonstd::string_view dynamic_linker = "";
 #endif
 
+void maybeFilterLinking(std::vector<nonstd::string_view> &new_args,
+                   nonstd::span<const nonstd::string_view> old_args, bool is_linking) {
+  if (!is_linking)
+    args::filterLinking(new_args, old_args);
+  else
+    for (auto arg : old_args)
+      new_args.push_back(arg);
+}
+
 int main(const bins::Info &info, nonstd::span<const nonstd::string_view> args) {
-  std::vector<nonstd::string_view> combined_args;
+  std::vector<nonstd::string_view> combined_args, combined_args_begin;
   if (!dynamic_linker.empty() && args::hasDynamicLinker(args)) {
-    combined_args.push_back("-dynamic-linker");
-    combined_args.push_back(dynamic_linker);
+    combined_args_begin.push_back("-dynamic-linker");
+    combined_args_begin.push_back(dynamic_linker);
   }
-  flags::appendFromString(combined_args, WRAPPER_LDFLAGS_BEFORE);
-  flags::appendFromVar(combined_args, VAR_PREFIX "_LDFLAGS_BEFORE");
+  flags::appendFromString(combined_args_begin, WRAPPER_LDFLAGS_BEFORE);
+  flags::appendFromVar(combined_args_begin, VAR_PREFIX "_LDFLAGS_BEFORE");
 
   std::vector<nonstd::string_view> initial_args;
   compiler::filterFlags(initial_args, args, remove_dynamic_linker);
@@ -50,14 +59,18 @@ int main(const bins::Info &info, nonstd::span<const nonstd::string_view> args) {
     flags::appendFromVar(combined_args, VAR_PREFIX "_LDFLAGS_DYNAMIC");
   }
 
-  std::vector<nonstd::string_view> filtered_args;
+  std::vector<nonstd::string_view> filtered_args, filtered_args_begin;
+  path::appendGood(filtered_args_begin, combined_args_begin, env::purePrefixes());
   path::appendGood(filtered_args, combined_args, env::purePrefixes());
 
+  const bool is_linking = args::isLinking(args);
   std::vector<nonstd::string_view> final_args;
+  maybeFilterLinking(final_args, filtered_args_begin, is_linking);
   state::Libs libs;
   const bool add_rpath =
       util::getenv(VAR_PREFIX "_LD_ADD_RPATH").value_or("1") == "1";
   if (dynamic && add_rpath) {
+    args::parseLibs(libs, filtered_args_begin);
     args::parseLibs(libs, filtered_args);
 #ifdef BUILD_DIR_ENV_VAR
     auto build_dir = util::getenv(BUILD_DIR_ENV_VAR);
@@ -72,11 +85,7 @@ int main(const bins::Info &info, nonstd::span<const nonstd::string_view> args) {
       final_args.push_back(rpath);
     }
   }
-  if (!args::isLinking(args))
-    args::filterLinking(final_args, filtered_args);
-  else
-    for (auto arg : filtered_args)
-      final_args.push_back(arg);
+  maybeFilterLinking(final_args, filtered_args, is_linking);
   return generic::main(info, final_args);
 }