Compilation fails on android 5

[nical]

Description

Older android targets do not compile anymore since the introduction of the android-properties dependency.

android-properties/src/android/mod.rs:68: error: undefined reference to '__system_property_read_callback'

Repro steps

I'm not sure how to make an android 5 build, I'll look in to it.

Extra materials

Link to the failing build on Firefox's CI: https://treeherder.mozilla.org/logviewer?job_id=382181918&repo=try&lineNumber=58241

Platform

Android 5

[nical]

After some digging the conclusion is that the property symbols from the android libc have to be loaded dynamically instead of linked statically. Gecko already does that in a few places. It's important to Firefox which ships a single binary that works on old and new Android devices (the oldest supported version is 4.4 I think).
Also I'm told that it's the recommended way short of using jni.

upstream PR: miklelappo/android-properties#1