A warning/note message for reminding people to clone submodule after the first clone.

[mergennachin]

🚀 The feature, motivation and pitch

At first trial, they forgot to clone with submodule → got error cannot find “gflags“ → they need to remember to clone submodule.

Alternatives

No response

Additional context

No response

RFC (Optional)

No response

cc @larryliu0820

[GregoryComer]

This may be more work than we want to do, but I've seen some projects lazy-clone submodules at build time. That also carries the advantage of only pulling submodules that we actually need. If you aren't building all of the various NPU backends, for example, you don't have to pull them down. I believe CMake also has some level of git integration to help with this.

Another closely related problem I've seen is forgetting to update submodules after pulling the latest ET. This can lead to weird build errors and sometimes takes me a few minutes to realize what's wrong. I'm not sure if there's a good way to detect this, though.

[mergennachin]

I just did a fresh clone, pulled in your PR (#8229) and tried install_executorch.sh, before the git submodule init/update steps.

Here's my error: https://gist.github.com/mergennachin/e218cfe00b4809a14d2a2ffe4abd61f4

In your Test Plan, you didn't actually test a fresh clone scenario.