shard-writer-v2: Make sure FALLOC_FL_COLLAPSE_RANGE is defined
shard-writer-v2: Make sure FALLOC_FL_COLLAPSE_RANGE is defined

FALLOC_FL_COLLAPSE_RANGE has only been available since 3.15, and our ARM
kernel is on 3.10. Make sure it's defined before compiling the fallocate
based code.

https://phabricator.endlessm.com/T13262

endlessm/eos-shard,endlessm/eos-shard,endlessm/eos-shard