Add android runner to run android binaries.

[Alexhuszagh]

Android binaries currently fail to run linking against certain dependencies, because libc++_shared.so is not found, so ensure the library is preloaded via LD_PRELOAD. This creates a simple android-runner file, so any additional changes can be added there.

This merely links to the proper libc++_shared.so, so it doesn't fix other issues. The hello world project now compiles and runs on aarch64-linux-android, but not i686-linux-android, which seems to be entirely unrelated (likely a permission error on the cloud Fedora server I'm running).

error getting old personality value: Operation not permitted
libc: error getting old personality value: Operation not permitted
Aborted (core dumped)

Linked Issues: #82

[Emilgardis]

would it be possible to add a runner to the ci?

[Alexhuszagh]

would it be possible to add a runner to the ci?

We already have a runner, but I believe to reproduce this error we require the cc dependency. rust-cpp-hello-world fails, but cargo init --bin --name hello . && cross run --target aarch64-linux-android passes.

Should we try to build against a project with a cc dependency in test.sh rather than just against an empty hello world project?

[Emilgardis]

we can make a new test repo for it to try on

[Emilgardis]

bors try --target android

[bors]

try

Build succeeded:

• conclusion

[Alexhuszagh]

This should be complete, I'm not sure if we need a 3rd party repository since we already test C++ support. The libc++_shared.so library is well documented, but we could use LD_LIBRARY_PATH instead if required. I think LD_PRELOAD is a better option. We also shouldn't need to provide LD_LIBRARY_PATH for /android-ndk/sysroot/usr/lib/$target/$ndk_version, which contains more complex logic (like vulkan, GLES layers, etc.), but I believe apps requiring this functionality are unlikely to run without a full Android emulator anyway.

[Emilgardis]

bors r+

[bors]

Build succeeded:

• conclusion