Humble attempt to add Cygwin support

It is working for me, but GUI never runs, this script is working flawlessly, though and so perhaps worth of merging...
On windows steps are:
1. install Cygwin
2. add adb binaries to system path to be runnable from everywhere
3. download this script, gaia.zip and b2g.tar.gz and run it through Cygwin terminal
If the separate character of Short options is `" "` (Line 29), then it should change to `"Darwin"|"CYGWIN"*)`.

The reason is this script will call `bash ./backup_restore_profile.sh -p${SP}${DEST_DIR} ...`.
There is no short options' separate character under Linux's bash, and the short options' separate character of Mac is space.