use -gstabs instead of -g (better gdb-on-windows support)

Change-Id: I906bb59cd1ce14eab0c4a8d872caddf6a0071c37
Reviewed-on: http://review.couchbase.org/27780
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>