This makes sure that newlib's printf is correctly overridden by:
1. Adding wrappers for some more obscure printf() variants
2. Forcing a compilation failure when newlib's stdio is still linked in
while mpaland-printf is used
3. Not adding `-u _printf_float` to the linker flags when mpaland-printf
is used.
This packs the stdio implementation from [1] as alternative to
what the used standard C lib provides with the intent to provide a
thread-safe, smaller, and more feature-complete alternative on
newlib targets.
Compared to `newlib_nano` this reduces `.text` by a bit more than 200 B
while adding support for standard format specifiers such as `RPIu8`,
`PRIu16`, `PRIu64`, `%z`, and `%t`.
Note that `newlib_nano`'s stdio can be thread-safe in reentrant mode
at the cost of RAM (per thread) and latency. Especially the increase
in latency can be prohibitive when real time requirements need to be
met.
[1]: https://github.com/mpaland/printf
