Log warnings to stdout instead of stderr

Currently, both stdout and stderr are redirected to a file. We want
stderr to be visible on the terminal in case the release config
fails, but we don't want to see the spam of warnings release config
always produces.

Move the warnings to stdout so they stay in the file when we start
showing stderr.

Test: m nothing
Change-Id: Ic869675f917270a472142b6e3a4210acaad7499b

cmd/release_config/release_config_lib/util.go

@@ -149,9 +149,12 @@ func DisableWarnings() {
 	disableWarnings = true
 }
 
+// warnf will log to stdout if warnings are enabled. In make code,
+// stdout is redirected to a file, so the warnings will not be shown
+// in the terminal.
 func warnf(format string, args ...any) (n int, err error) {
 	if !disableWarnings {
-		return fmt.Fprintf(os.Stderr, format, args...)
+		return fmt.Printf(format, args...)
 	}
 	return 0, nil
 }