std.Build: avoid use of catch unreachable

Usage of `catch unreachable` in build scripts is completely harmless
because build scripts are always run in Debug mode, however, it sets a
poor example for beginners to learn from.
90e48d4b34Andrew Kelley committed on 1/31/2023, 10:09:35 PMparent13a9616
13 files changedLine totals unavailable