This reverts commit e240d81ff8 and
introduces a more compatible method of finding newly added fish scripts
to syntax check.
`find -newer` is the original and is supported by everything under the
sun (including FreeBSD, NetBSD, Solaris, OpenIndiana, macOS 10.10, WSL,
and more), and if not, the tests will succeed anyway. `find -mnewer` was
added later around the time `find -cnewer` and co (which checks the
creation date rather than the modification date) was introduced, but
apparently the GNU version of coreutils never introduced the `-mnewer`
alias for `-newer`.
Yes, this is hacky and yes it would be ideal if the build system is the
one that picked which tests to run rather than the test itself picking.
But let's not pretend that our tests are idealogically ideal or pure
right now and until we fix the mess that is our CMake test integration
(e.g. use ctest and configure each test to be run separately with
configurable payloads, etc) eight seconds is still eight seconds, and
again, the CI isn't affected.