Can't run example 28 (cloth simulation) and voxel challenge examples

[neozhaoliang]

UPDATE: the same problem also happens for example 28 mass_spring_3d_ggui.

Using the current master branch (commit 945c6f43f81244f676667693b027066fd0836dc1) I cannot run the voxel-challenge examples: https://github.com/taichi-dev/voxel-challenge

For all examples in the repo the window got stuck and shows

But using v1.1.0 works fine for me.

[bobcao3]

It could just be slow...

[neozhaoliang]

@bobcao3 I tested with v1.1.0, and all the examples work fine.