CUB when installing inside tutorials

Summary:
We now require CUB for building, here we make the tutorials include it.

Also make the installation cell do nothing if it has already succeeded.

I use curl not wget, and `os.environ` to set the variables not shell methods, because they are more likely to work on Windows.

Reviewed By: nikhilaravi

Differential Revision: D24860574

fbshipit-source-id: 5be86af15e53f8db016ee0e96fb43153bd69adbc

docs/tutorials/render_textured_meshes.ipynb

@@ -65,12 +65,22 @@
    "outputs": [],
    "source": [
     "!pip install torch torchvision\n",
+    "import os\n",
     "import sys\n",
     "import torch\n",
     "if torch.__version__=='1.6.0+cu101' and sys.platform.startswith('linux'):\n",
     "    !pip install pytorch3d\n",
     "else:\n",
-    "    !pip install 'git+https://github.com/facebookresearch/pytorch3d.git@stable'"
+    "    need_pytorch3d=False\n",
+    "    try:\n",
+    "        import pytorch3d\n",
+    "    except ModuleNotFoundError:\n",
+    "        need_pytorch3d=True\n",
+    "    if need_pytorch3d:\n",
+    "        !curl -O https://github.com/NVIDIA/cub/archive/1.10.0.tar.gz\n",
+    "        !tar xzf 1.10.0.tar.gz\n",
+    "        os.environ[\"CUB_HOME\"] = os.getcwd() + \"/cub-1.10.0\"\n",
+    "        !pip install 'git+https://github.com/facebookresearch/pytorch3d.git@stable'"
    ]
   },
   {