apko: install using git-checkout to get version info

[imjasonh]

Fixes #825

This changes the build from using go/install to using git-checkout and runs: make ... so that Git version info is available to be injected into the binary using ldflags.

This also adds an explicit build-time dependency on go (previously implicit from using go/install), and removes the explicit build-time dep on git (now implicit from using git-checkout).

This also removes the runtime dependency on apk-tools, which is no longer necessary since v0.7.0.

Pre-review Checklist

For new package PRs only

• This PR is marked as fixing a pre-existing package request bug
  • Alternatively, the PR is marked as related to a pre-existing package request bug, such as a dependency
• REQUIRED - The package is available under an OSI-approved or FSF-approved license
• REQUIRED - The version of the package is still receiving security updates

For security-related PRs

• The security fix is recorded in annotations and secfixes

For version bump PRs

• The epoch field is reset to 0
• Patch source: patch source here