bugfix: print version to stderr on startup (#6172)

Unlike the rest of the normal startup output (which goes to stderr), the
version number is being printed to stdout, which makes it harder to
ignore all of firejail's output.  Example:

    $ firejail --noprofile /usr/bin/true --version 2>/dev/null
    firejail version 0.9.73

    true (GNU coreutils) 9.4
    Copyright (C) 2023 Free Software Foundation, Inc.
    License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.

    Written by Jim Meyering.

So make the normal startup version output go to stderr and keep the
other occurrences (such as in `firejail --version`) going to stdout, to
make it easier to grep things in the output.

Added on commit f019f0ec3 ("Print version on startup for
firejail/firecfg", 2023-05-11) / PR #5829.

Reported by @rusty-snake[1].

[1] https://github.com/netblue30/firejail/issues/6171#issuecomment-1912768721

1 files changed, 1 insertions, 1 deletions

diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index d76a6c0ee..eb9287f2e 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -492,7 +492,7 @@ void tree(void);
 void top(void);
 
 // usage.c
-void print_version(void);
+void print_version(FILE *stream);
 void print_version_full(void);
 void usage(void);