main/haproxy: upgrade to 2.1.8

change make TARGET to linux-musl, it is supported now
7 jobs for !12185 with 3.12-stable-haproxy-2.1.8 in 3 minutes and 51 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed #219617
docker-alpine x86_64
lint

00:00:23

 
  Build
passed #219622
docker-alpine ci-build aarch64
build-aarch64

00:03:25

passed #219623
docker-alpine ci-build armv7
build-armv7

00:02:53

passed #219621
docker-alpine ci-build ppc64le
build-ppc64le

00:03:02

passed #219620
docker-alpine ci-build s390x
build-s390x

00:01:25

passed #219619
docker-alpine ci-build x86
build-x86

00:01:38

passed #219618
docker-alpine ci-build x86_64
build-x86_64

00:01:35