loader: suggest to install the right kernel devel package

Unfortunately, some package dependency system do not allow to make
sure that the kernel development package installed is the same version
as the running kernel. When this happen, the loader, unable to find
the kernel header, will suggest to rebuild the kernel with
CONFIG_IKHEADERS. For most users, this is probably not an option, but
installing the kernel development package corresponding to the running
kernel version is.

src/cc/frontends/clang/loader.cc

@@ -151,7 +151,8 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, TableStorage &ts,
       kpath = tmpdir;
     } else {
       std::cout << "Unable to find kernel headers. ";
-      std::cout << "Try rebuilding kernel with CONFIG_IKHEADERS=m (module)\n";
+      std::cout << "Try rebuilding kernel with CONFIG_IKHEADERS=m (module) ";
+      std::cout <<  "or installing the kernel development package for your running kernel version.\n";
     }
   }