Set py3.x build-environment name consistently (#122247)
https://github.com/pytorch/pytorch/pull/122157 checks for the Python version using `"$BUILD_ENVIRONMENT" != *py3.8*`, but some build environment uses a different style with `py3_8` instead causing numpy 2.x to be installed there wrongly, i.e. https://hud.pytorch.org/pytorch/pytorch/commit/03b987fe3fa93f398c0af5b40e512950c39a7cb6
Pull Request resolved: https://github.com/pytorch/pytorch/pull/122247
Approved by: https://github.com/malfet
