Add build date to build cmd

Author: ponsfrilus

.travis.yml

@@ -24,7 +24,7 @@ script:
 # - go get -v ./...
 # - diff -u <(echo -n) <(gofmt -d .) # can't make gofmt ignore vendor directory
 # - go vet $(go list ./... | grep -v /vendor/)
-  - if [ "${LATEST}" = "true" ]; then gox -os="linux darwin windows" -arch="amd64" -output="lazygit.." -ldflags "-X main.Rev=`git rev-parse --short HEAD`" -verbose ./...; fi
+  - if [ "${LATEST}" = "true" ]; then gox -os="linux darwin windows" -arch="amd64" -output="lazygit.." -ldflags "-X main.Rev=`git rev-parse --short HEAD` -X main.builddate=`date -u +%Y%m%d.%H%M%S`" -verbose ./...; fi
 deploy:
   provider: releases
   skip_cleanup: true