Move versioning to `ldflags`

[severindellsperger]

As mentioned by @jklaiber, the application versioning can be moved to ldflags instead of changing it manually in the internal\version.go file.

Originally posted by @jklaiber in #15 (review)

[severindellsperger]

Probably that works:

GOARCH=${GOARCH} GOOS=${GOOS} go build -ldflags "-s -w -X 'gokard/cmd.version=${VERSION}'" -trimpath -o ${BUILD_DIRECTROY}/${BINARY_NAME} main.go