Mixing address spaces is something LLVM doesn't like (for good
reason). This re-organized the code a bit so that this does not
happen anymore, even on AVR.
Split out of https://github.com/RIOT-OS/RIOT/pull/16924
When double-checking the error codes provided by newlib by default
(without magic defines, such as `__LINUX_ERRNO_EXTENSIONS__` or
`__CYGWIN__`), some where still missing in `tiny_strerror()`. This
adds the missing ones.
`tiny_strerror()` is a drop-in replacement for `strerror()`, but
instead of a long help message it returns the much shorter macro name
matching the given number.
The (pseudo-)module `tiny_strerror_as_strerror` can be used to
replace all calls to `strerror()` with calls to `tiny_strerror()`.
