Update version.txt file path (pytorch#61177)

Summary:
The file version.txt is located one directory above generate_torch_version,
some platforms are unable to find this file unless given an explicit
path.

Pull Request resolved: pytorch#61177

Reviewed By: pbelevich

Differential Revision: D29660334

Pulled By: ezyang

fbshipit-source-id: f66105f782aaff031e373f96a69baabb13c89337

tools/generate_torch_version.py

@@ -13,7 +13,7 @@ def get_sha(pytorch_root: Union[str, Path]) -> str:
 
 def get_torch_version(sha: Optional[str] = None) -> str:
     pytorch_root = Path(__file__).parent.parent
-    version = open('version.txt', 'r').read().strip()
+    version = open(pytorch_root / 'version.txt', 'r').read().strip()
 
     if os.getenv('PYTORCH_BUILD_VERSION'):
         assert os.getenv('PYTORCH_BUILD_NUMBER') is not None