cxxmodules: clang-scan-deps needs -resource-dir when cross compiling

with the latest cmake 3.28 with module support enabled, when cross compiling with clang, it's better to supply the rsult of clang++ -print-resource-dir as -resource-dir otherwise might run into this: https://clang.llvm.org/docs/StandardCPlusPlusModules.html#possible-issues-failed-to-find-system-headers