try_build_id_prefix gcc-10 -Wformat-security errors

try_build_id_prefix gcc-10 -Wformat-security errors

dwarf.c:11300:3: error: format not a string literal and no format arguments [-Werror=format-security]
11300 |   f += sprintf (f, prefix);

	PR 28697
	* dwarf.c (try_build_id_prefix): Avoid -Wformat-security error.