external dep lib dir

interfaces/Crafter.Build-External.cppm

@@ -43,6 +43,13 @@ export namespace Crafter {
         ExternalBuilder builder = ExternalBuilder::None;
         std::vector<std::string> options;
         std::vector<fs::path> includeDirs;
+        // Extra library search paths (each becomes a -L flag), interpreted
+        // relative to the CMake build dir. Currently only honoured for
+        // ExternalBuilder::CMake. The CMake builder always adds its
+        // top-level build dir as a -L; libDirs is for projects (msquic,
+        // others) whose CMakeLists set LIBRARY_OUTPUT_DIRECTORY to a subdir
+        // of the build tree.
+        std::vector<fs::path> libDirs;
         std::vector<std::string> libs;
     };