Support specifying a torch range (#8936)

Co-authored-by: Nicolas Hug <[email protected]>
Co-authored-by: Nicolas Hug <[email protected]>

Author: oraluben

setup.py

@@ -96,8 +96,14 @@ def get_dist(pkgname):
             return None
 
     pytorch_dep = os.getenv("TORCH_PACKAGE_NAME", "torch")
-    if os.getenv("PYTORCH_VERSION"):
-        pytorch_dep += "==" + os.getenv("PYTORCH_VERSION")
+    if version_pin := os.getenv("PYTORCH_VERSION"):
+        pytorch_dep += "==" + version_pin
+    elif (version_pin_ge := os.getenv("PYTORCH_VERSION_GE")) and (version_pin_lt := os.getenv("PYTORCH_VERSION_LT")):
+        # This branch and the associated env vars exist to help third-party
+        # builds like in https://github.com/pytorch/vision/pull/8936. This is
+        # supported on a best-effort basis, we don't guarantee that this won't
+        # eventually break (and we don't test it.)
+        pytorch_dep += f">={version_pin_ge},<{version_pin_lt}"
 
     requirements = [
         "numpy",