Add a tag '_speed_buildx_for_cgo_alpine' for Dockerfiles:
1. require golang with CGO_ENABLED=1
2. use alpine image.
So used in 'build/lc/Dockerfile'
Signed-off-by: llhuii <liulinghui@huawei.com>
We use docker-buildx to build our components images for different
platforms.
But for some languages, such as golang, have good builtin build for
multi platforms, and buildx support that.
In Sedna, we have GM/LC written by golang. This commit supports this
function.
Signed-off-by: llhuii <liulinghui@huawei.com>