[M8] reusable libraries: install layout + cargoxx-path deps

tests/e2e/buildCppPackage/src/bin/extra.cpp

@@ -0,0 +1,8 @@
+#include <nlohmann/json.hpp>
+import std;
+int main() {
+    nlohmann::json j;
+    j["from"] = "extra";
+    std::println("{}", j["from"].get<std::string>());
+    return 0;
+}