Compilation: move comptime condition first

Avoids compile error on Windows due to not having execv capabilities.

Fixup for eb3f7d2f37cab1d3df7c4493b8239e802b83e521.

See #6768
a9af472728Andrew Kelley committed on 8/24/2022, 10:19:31 PMparent07afd5b
1 file changedLine totals unavailable