Use external main module

* renames main package so it's importable
* adds wrapmain sub-module as main module

Dockerfile

@@ -14,7 +14,7 @@ COPY go.sum /go-ethereum/
 RUN cd /go-ethereum && go mod download
 
 ADD . /go-ethereum
-RUN cd /go-ethereum && go run build/ci.go install -static ./cmd/geth
+RUN cd /go-ethereum/wrapmain && go build --trimpath -o /go-ethereum/build/bin/geth .
 
 # Pull Geth into a second stage deploy alpine container
 FROM alpine:latest