The check calls sceKernelFstat and uses the Windows directory descriptors, so on Linux the test target no longer linked; its CMake links libkernel only on Windows.
A guest that reopens `stdin`, `stdout` or `stderr` onto a directory in a read mode threw instead of
returning the stream, while the console answers that a directory opens in a read mode and the
debt entry already recorded the throw as the Windows difference.
The standard stream now goes through the same descriptor move a regular file uses: the directory
descriptor is opened, moved onto the standard descriptor, and libkernel's directory entry follows
it, so `fstat` of the guest descriptor reports a directory and the first read answers `EISDIR` with
the error indicator set, like every other directory stream. A failed open restores the previous
standard target.
`guest_freopen_host_standard` reopens `stdout` onto a directory, asserts `S_IFDIR` on the guest
descriptor, asserts the first read answers `EISDIR`, then reopens the same stream on a file path
and writes through it.
freopen of an empty name on stdout fails with ENOENT as fopen of an empty name does, the guest stream is closed afterwards and the host standard output is still writable and still reaches its destination. Before the previous commit the call failed with EINVAL.
Dean Galvin