[Cmake] Drop quotation marks around `$ENV{MAX_JOBS}` (#44557)
Summary:
Solves `the '-j' option requires a positive integer argument` error on some systems when MAX_JOBS is not defined
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44557
Reviewed By: vkuzo
Differential Revision: D23653511
Pulled By: malfet
fbshipit-source-id: 7d86fb7fb6c946c34afdc81bf2c3168a74d00a1f