* Bump to golang-with-libgit2:1.1.1.6 to speed up build time when cross compiling. Previous version was compiling in emulation mode instead, which added +10x overhead.
* Ensure that make test is executed against the exact same libraries that will be shipped on the built image.
* Simplify Makefile to reduce its complexity.
* Libgit2 behaviour:
linux-amd64 download static libraries from the official container image.
linux-arm64 on top of the above, requires static musl tool chain (automatically downloaded).
darwin-amd64 and darwin-arm64 download universal static libraries for darwin from https://github.com/fluxcd/golang-with-libgit2 releases.
Co-authored-by: Paulo Gomes <paulo.gomes@weave.works>
Signed-off-by: Sanskar Jaiswal <sanskar.jaiswal@weave.works>