I love C and wrote some CGIs in C in the past but I don't love concurrent programming in C. While forking and execing can use shared read-only mmap on .text segments, the .bss and .data will need initialization and copying; there's unavoidable startup overhead that a threaded process avoids, and raw pthreads is kind of painful. If all you need to do is serve a low traffic site, CGI is fine.
My biggest worry would be how often the SQLite DB gets backed up because there's no way a C web server will be free of RCEs in today's world.