main/lxc: add init.lxc.static

this is needed for lxc-execute to work
add libcap-static to makedepends
fixes #10821
5 jobs for !128 with lxc-3.2.1-r1 in 8 minutes and 57 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed #1119
docker-alpine x86_64
lint

00:00:20

 
  Build
passed #1123
docker-alpine ci-build ppc64le
build-ppc64le

00:01:14

passed #1122
docker-alpine ci-build s390x
build-s390x

00:08:36

passed #1121
docker-alpine ci-build x86
build-x86

00:01:46

passed #1120
docker-alpine ci-build x86_64
build-x86_64

00:01:38