Prepare image for build including aarch64-linux-musl-cross

[shiki-tak]

If we decide to prepare our Docker image, we will respond. If not, please close.

I need aarch64-linux-musl-cross for the wasmer build, but the github actions refuse to get it from musl.cc using wget.

Therefore, I use the image that already contains this as a builder and copy and use it.
https://github.com/line/wasmvm/pull/71/files#diff-a3e40ace4c88526a8320154b12cfc19c7b048c6fd2ea67ddddb3e4849711f249R10

If we should prepare our own Docker image beforehand without using this, then I think this is a matter for another issue.

Originally posted by @shiki-tak in #71 (comment)

[tnasu]

It should do what we are since it doesn't need to compile and create a Docker image every time with our specific environment before we build wasmvm.