macos-builder02 in particular has been having problems for a while now
that no one could reproduce. We believe we have finally found the cause:
missing shebangs, not just in the tests themselves but *also* in the
inline scripts `nix-shell` itself writes.
Fixes#1042.
I believe this will also fix#1093.
See also: https://github.com/NixOS/nix/pull/14778
Change-Id: I54d04a770b8e78484815db88a8bc88776a6a6964
This change feels kind of gross and reveals a fair bit about the
disorganization of our tests, but I think it makes parts of it a bit
better.
Change-Id: Idb8d9a00cbd75d5c156678c6b408b42b59d5e4d7