Statically build using musl toolchain and target alpine

[pjbgf]

Main changes:

• Statically build controller using musl toolchain.
• Simplifies Dockerfile by leveraging the musl toolchain static libraries provided by golang-with-libgit2@libgit2-1.1.1-4.
• Target alpine as final base image.

Although the controller is statically built, we are targeting alpine to help users debugging the image if they so need/wish.

[stefanprodan]

@pjbgf I'm not for changing the runtime image in this release. Users will not be able to debug SC nor IAC if we use distroless since there is no shell so they can't see if tmp gets filled, or test egress or list artifacts. Please use Alpine or Bookwarm.

[hiddeco]

➕ around Stefan's concerns, but no specific preference for an alternative image.

[pjbgf]

@stefanprodan fair point - I will stick to Alpine as it is less than 10% of the size of bookworm-slim.

[stefanprodan]

LGTM

Thanks @pjbgf 🏅