Version 1274 was commited by markb on 2009-10-10 18:42:14 +0100 (Sat, 10 Oct 2009) Open the files to be included in gmapsupp.img using read-only mode. It was opening the files using read-write mode but that fails if any files are not capable of being written. As the files are not going to be written while producing gmapsupp.img, just open them read only.