[M5] verify-curated-db.sh + boost recipe (header-only)

scripts/curated-snippets/cxxopts.cpp

@@ -0,0 +1,8 @@
+#include <cxxopts.hpp>
+import std;
+
+int main() {
+    cxxopts::Options opts("verify", "verify cxxopts");
+    std::println("cxxopts ok: {}", opts.program());
+    return 0;
+}