testing/xmrig: upgrade to 6.12.1

Ref https://github.com/xmrig/xmrig/releases/tag/v6.12.1
7 jobs for !20757 with xmrig in 3 minutes and 51 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed #378045
docker-alpine x86_64
lint

00:00:19

 
  Build
passed #378050
docker-alpine ci-build aarch64
build-aarch64

00:01:15

passed #378051
docker-alpine ci-build armv7
build-armv7

00:00:35

passed #378049
docker-alpine ci-build ppc64le
build-ppc64le

00:00:43

passed #378048
docker-alpine ci-build s390x
build-s390x

00:01:29

passed #378047
docker-alpine ci-build x86
build-x86

00:01:07

passed #378046
docker-alpine ci-build x86_64
build-x86_64

00:00:51