Remove empty initializers to ensure MSVC compatibility.

Add -Wgnu-empty-initializer to Clang builds to catch this issue in the future. Initialising arrays with empty braces is not part of the C standard and fails on MSVC. This commit should catch the issue earlier by detecting it in Clang.

PiperOrigin-RevId: 517373961
Change-Id: I518006e84151e8d5b45a7fe00ba7675dfb031ca0

src/engine/engine_collision_driver.c

@@ -222,8 +222,8 @@ void mj_collideTree(const mjModel* m, mjData* d, int b1, int b2,
   const mjtNum* bvh2 = m->bvh_aabb + 6 * bvhadr2;
   const int* child1 = m->bvh_child + 2 * bvhadr1;
   const int* child2 = m->bvh_child + 2 * bvhadr2;
-  mjtNum product[36] = {};  // 2 bb x 2 bb x 3 axes (body) x 3 axes (world)
-  mjtNum offset[12] = {};   // 2 bb x 2 bb x 3 axes (world)
+  mjtNum product[36];  // 2 bb x 2 bb x 3 axes (body) x 3 axes (world)
+  mjtNum offset[12];   // 2 bb x 2 bb x 3 axes (world)
   mjtByte initialize = 1;
 
   mjMARKSTACK;