Preserve file sparsity in FdFile::Copy

Use lseek SEEK_DATA / SEEK_HOLE in FdFile::Copy to avoid writing empty
blocks. This helps to save disk space on file systems that support
sparse files.

Test: art/tools/run-gtests.sh
Change-Id: Idb9202f4b9473c79225a9301bebd495c80bd6558
2 files changed