[doranteseduardo]

Summary

Fixes two bugs from issues: an Android crash when a scene mounts a ViroARCamera (#597 in viro), and GLB characters with several skins on the same joints losing joint rotations (#599 in viro).

Android: JavaVM set in JNI_OnLoad (VROPlatformUtil.cpp)

• libviro_renderer.so had no JNI_OnLoad. sVM was set only when a renderer or a loader called VROPlatformSetEnv.
• Under Fabric, React builds VRTCamera's view before the navigator's renderer. Adding its node calls nativeUpdateAtomicUmbrellaBounds, which reaches getJNIEnv with no VM, and the assertion fails with a SIGSEGV.
• The library is loaded with System.loadLibrary("viro_renderer"), so JNI_OnLoad now sets the VM before anything else runs. VROPlatformSetEnv keeps setting it as before, with the same value.

GLB: shared joints keep every property (VROGLTFLoader.cpp)

• resampleSkeletalChannelsToCommonGrid runs once per (animation, skin) and writes each joint's merged channel back in place.
• When a later skin shares those joints, it re-merges the already-merged channel. The if / else if chain copied only the first property it found (translation), so those joints fell back to their rest-pose rotation and scale.
• Every property of a channel is now copied, which makes the merge idempotent. Re-sampling a merged track onto a later skin's grid is lossless: that grid includes the merged track's times.

Notes

• The issue reporter suggested an optional per-animation set of already-merged joints. It isn't included here: a later skin with different joints builds a different grid, and skipping shared joints would leave tracks of different lengths in one skin.
• CHANGELOG and RELEASE_NOTES (3.1.0) updated.

Testing

• Built with scripts/build.sh (Android AAR, iOS device and simulator). JNI_OnLoad is exported from libviro_renderer.so in arm64-v8a and armeabi-v7a.
• The rebuilt binaries ship in viro's companion PR.