Add a "deps" attribute to cc_import

[pylaligand]

Description of the problem / feature request:

This is a feature request to add a deps attribute to cc_import.

Feature requests: what underlying problem are you trying to solve with this feature?

Some prebuilt libraries have public dependencies on other libraries, by using these libraries' public headers in their own public headers. There currently does not seem to be a way to express this with cc_import which is the preferred way to include prebuilts.

Have you found anything relevant by searching the web?

There's a way to work around this by declaring a cc_library which both depends on the cc_import and on its public dependencies, and direct clients to depend on the cc_library.

[hlopko]

Good point, we'll fix it. But to save cycles let's do so only after cc_import is in Skylark (blocked by #4570).

[MSK61]

The attribute is still not documented here though.