lucihttp: update to latest Git HEAD

Fixes compilation under 32bit systems by using the proper printf format
specifier for size_t values.

Also fixes compilation with Ninja by appending instead of
overwriting CMAKE_OPTIONS.

Fixes: #5116
Suggested-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Jo-Philipp Wich <jo@mein.io>