libc: minimal: print stderr just like stdout

So far data that went to stderr was simply dropped in case of minimal
libc. In case of newlib stderr was treated same like stdout
(e.g. fprintf(stderr, ...) was equivalent to fprintf(stdout, ...).

Extend filter on stream pointer to allow both stdout and stderr to pass
data to stdout hook (which is Zephyr console backend in most cases).

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
1 file changed