Build a binary with --replace doesn't work

[lexbritvin]

When using --replace flag an error is produced

launchr build --no-cache -t 500s --tag nethttpomithttp2 -vvv \
-p github.com/launchrctl/launchr@latest \
-p github.com/launchrctl/compose@latest \
-p github.com/launchrctl/keyring@latest \
-p github.com/launchrctl/web@multistep-2 \
--replace "github.com/launchrctl/web=/my/path"
-n launchr -o launchr-web --build-version v0.0.0

Result:

 INFO  Generating the go files
 INFO  Running plugin generation
gen.go:11:2: module github.com/launchrctl/web provides package github.com/launchrctl/web and is replaced but not required; to add it:
	go get github.com/launchrctl/web
  ERROR   exit status 1

[lexbritvin]

Fixed in #102