Fiasco.OC: fix run-environment for ARM platforms

Eliminate prints to stderr for normal messages, because it leads to exceptional
returns in TCL-scripts e.g. when run-script is triggered by the autopilot even
if the script's return code itself will be zero.

base-foc/run/env

@@ -185,13 +185,13 @@ proc build_boot_image_arm {binaries} {
 	set pid [eval "spawn sh -c \"$gen_img_cmd\""]
 	expect { eof { } }
 	if {[lindex [wait $pid] end] != 0} {
-		puts "Error: Single-image creation failed"
+		puts stderr "Error: Single-image creation failed"
 		exit -4
 	}
 
 	exec cp [bin_dir]/bootstrap.elf [run_dir]/image.elf
 
-	puts stderr "\nboot image: [run_dir]/image.elf\n"
+	puts "\nboot image: [run_dir]/image.elf\n"
 }