Draft: Build virglrenderer in-tree for AOSP
This MR collects some experimental changes to build virglrenderer in-tree for Android, with the goal of using the latest upstream virglrenderer code in external/virglrenderer
in an AOSP tree.
Some of the changes are inspired by the AOSP fork of virglrenderer at https://android.googlesource.com/platform/external/virglrenderer/