Fix regression with android_exe_type

[dcbaker]

I think this is simply a case where the code that converted the executable arguments to shared_library arguments happened to work, but wasn't exactly correct. I've attempted to make the conversion robust, but I don't have an Android cross setup to test with.

Fixes: #15238

[dcbaker]

@sp1ritCS: I don't have a setup to test, but just by inspection I think I found the issue, but I'd appreciate if you could test that this works for you.

[sp1ritCS]

Negative, the error still occurs. I've done some basic printf debugging (logging what gets set in the sh_kwarg loop) and the problem is that the RUST_ABI arg isn't part of EXCLUSIVE_SHARED_LIB_KWS :)

[bonzini]

This should work but on top of this the rust_crate_type should be changed to 'cdylib' if it is None, otherwise the default will be Rust ABI.

[dcbaker]

I would have thought it would have done what @bonzini said, but I've made it explicitly set the rust_abi and rust_crate_type as we would expect now.

[sp1ritCS]

This works now. Tho I guess it is less "robust" that the commit header makes it out to be, in case _EXCLUSIVE_LIB_KWS gets extended.

Perhaps @jpakkane can be nudged to build and upload a container providing a NDK toolchain. We have a setup script for our container which may be adopted (Tho we moved away from a Dockerfile to fdo-ci-templates to avoid dealing with building containers outself). Just seen that the container defs are just part of the meson repo itself, I guess I can just submit it myself 🙃

[dcbaker]

I looked into why it's doing what it's doing, and both @bonzini and I were off because the default for rust_abi and rust_crate_type is None, which will default to using rust_abi == 'rust, which turns into dylib`.

The robustness thing is true though, since it fills in all of the shared library fields that that are expected.

[dcbaker]

Maybe that should be broken into two patches?

[bonzini]

I think this PR is good as is, except for possibly adding a similar loop involving _EXCLUSIVE_LIB_KWS.

[dcbaker]

I had another idea, I think this is even a little better, @bonzini let me know what you think.

[bonzini]

Oh yeah, that makes a lot of sense!