Add support for building with llhttp instead of http-parser #90

Job	Run time
build (fedora:latest, true)	1m 1s
build (centos:7, true)	1m 23s
build (quay.io/centos/centos:stream8, true)	1m 29s
build (quay.io/centos/centos:stream9, true)	1m 39s
build (debian:testing, true)	40s
build (debian:latest, true)	41s
build (ubuntu:rolling, true)	49s
build (ubuntu:lunar, true)	43s
build (ubuntu:jammy, true)	43s
build (ubuntu:focal, true)	39s
build (ubuntu:bionic, true)	1m 0s
build (quay.io/fedora/fedora:rawhide, false)	55s
build (ubuntu:devel, false)	49s
	12m 31s

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