[cmake] build fcgi-auth, fcgi-responder for tests

Aside: must have cmake enable building openssl for tests to pass
due to tests/lighttpd.conf including config options requiring openssl
algorithms in mod_secdownload.c:
  (secdownload.algorithm       = "hmac-sha1")
  (secdownload.algorithm       = "hmac-sha256")

$ cmake -L .
$ cmake -DWITH_OPENSSL:BOOL=ON .
$ make -j 4 -k
$ make test

x-ref:
  https://blog.lighttpd.net/articles/2006/12/25/1-5-0-goes-cmake/

tests/CMakeLists.txt

@@ -1,3 +1,15 @@
+check_include_files(fastcgi.h HAVE_FASTCGI_H)
+check_include_files(fastcgi/fastcgi.h HAVE_FASTCGI_FASTCGI_H)
+if(HAVE_FASTCGI_H OR HAVE_FASTCGI_FASTCGI_H)
+	check_library_exists(fcgi FCGI_Accept "" HAVE_FASTCGI)
+	if(HAVE_FASTCGI)
+		add_executable(fcgi-auth fcgi-auth.c)
+		add_executable(fcgi-responder fcgi-responder.c)
+		target_link_libraries(fcgi-auth fcgi)
+		target_link_libraries(fcgi-responder fcgi)
+	endif()
+endif()
+
 set(T_FILES
 	prepare.sh
 	cachable.t