Turn off CRC checking for append2simg

make_ext4fs doesn't write out a CRC chunk, and append2simg doesn't
either, but append2simg was still performing a CRC on every input
block.  Cuts append2simg time in half.

Change-Id: I678f807abbb741042461ed68a0f61b406d3665fb

libsparse/append2simg.c

@@ -82,7 +82,7 @@ int main(int argc, char *argv[])
         exit(-1);
     }
 
-    sparse_output = sparse_file_import_auto(output, true, true);
+    sparse_output = sparse_file_import_auto(output, false, true);
     if (!sparse_output) {
         fprintf(stderr, "Couldn't import output file\n");
         exit(-1);