common : make build info output stream configurable (#28322)

Let llama_print_build_info write to a caller-provided FILE* instead of
hardcoding stderr. The parameter defaults to stderr so existing callers
keep their current behavior.

The version command in llama-app now passes stdout, so plain version
output goes to stdout where users expect it.

Signed-off-by: Adrien Gallouët <angt@huggingface.co>

app/llama.cpp

@@ -80,7 +80,7 @@ static const command cmds[] = {
 #undef UPDATE_HIDDEN
 
 static int version(int /*argc*/, char ** /*argv*/) {
-    llama_print_build_info(llama_version());
+    llama_print_build_info(llama_version(), stdout);
     return 0;
 }