c-accel: add compile_flags.txt for clangd Without the Tarantool include path, clangd can't find <module.h> and the entire file cascades into undefined-symbol diagnostics. The actual make build is unaffected — only the editor experience. List the four common Tarantool include paths (macOS Homebrew, the Cellar-style symlink, /usr/local, /usr/include). Missing dirs are silently ignored by the compiler, so a single file works for both macOS and Linux.