fixing flag to skip nvfuser_tests build (#93080)
Slowly pushing cmake cleanup to upstream.
avoids building nvfuser_tests when BUILD_TEST is disabled.
nvfuser_tests uses googletest from pytorch, which is only dragged when BUILD_TEST is enabled.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93080
Approved by: https://github.com/davidberard98, https://github.com/huydhn, https://github.com/malfet
