unconditionally generate lockfile

[japaric]

Right now, something like this produces an error:

$ cargo add foo
$ cross build
error: failed to write /project/Cargo.lock

Caused by:
  failed to open: /project/Cargo.lock

[Emilgardis]

There doesn't seem to be a way to replicate cargo build when it adds new deps. Closest match is cargo update, but that can also update deps.

[japaric]

cargo generate-lockfile does the trick, I think, if you call it before cross build. I don't think it updates dependencies; it just adds new dependencies and changes their paths/git urls if necessary.

[tbu-]

Looks like this was fixed in 0.1.5.

[Arzte]

I'm still seeing this issue, using the latest version. Here's a log https://travis-ci.org/mgattozzi/alchemist/jobs/204565275#L524

[Emilgardis]

You should let cross do it with cross build/run, with cross generate-lockfile you are telling cargo to generate a lockfile inside the read-only docker image.

[Arzte]

The error still shows up with that not there, I added it to test if it would help, I'll remove it and try again though...
https://travis-ci.org/mgattozzi/alchemist/jobs/204644806#L524

[Emilgardis]

I think #67 is the cause, cargo fetch is run, but somehow cargo still complains. I think we need to run cargo fetch --target <target-triple> [...] to make this work. Not sure.

This issue should be reopened.

[japaric]

OK. I think I found the problem. This is a workspace so cargo fetch is producing a Cargo.lock in the root of the workspace but when you call cd alchemist && cross build --target $T, Cargo tries to create a new Cargo.lock in that directory.

Using cross build --target $T -p alchemist from the root of the repository seems to at least produce / use the right Cargo.lock and starts the build process (then it fails to link with /usr/bin/ld: cannot find -lsqlite3 but that's a totally different problem)

[Arzte]

Its looking for sqlite3 since that (for the moment) is the database we are using for alchemist.
So this should be fine if we just use -p whicheverproject is getting built then?