[M5+] nix-cmake-scan walks the dev output for multi-output packages

src/resolver/resolver.cppm

@@ -10,11 +10,17 @@ export namespace cargoxx::resolver {
 
 // What `nix eval nixpkgs#<pkg>` reports for a package: a confirmation that
 // the attribute exists, a best-effort version string, and the realized
-// nix-store path so later probes can scan its installed CMake configs.
+// nix-store path(s) so later probes can scan its installed CMake configs.
+//
+// Multi-output packages (boost, openssl, llvm, ...) expose CMake configs
+// in their `dev` output, not in the default `out`. When the package has
+// a separate dev output its store path is captured here so callers can
+// scan it preferentially.
 struct NixpkgsInfo {
-    std::string attr;       // the queried name, e.g. "simdjson"
-    std::string version;    // empty when the derivation has no version
-    std::string out_path;   // absolute /nix/store/... path
+    std::string attr;        // the queried name, e.g. "simdjson"
+    std::string version;     // empty when the derivation has no version
+    std::string out_path;    // default output's absolute /nix/store/... path
+    std::string dev_path;    // dev output's path; empty when no dev output
 };
 
 // Pure parser exposed for unit testing. Accepts the raw JSON returned by