Gong Heng authored Mar 18, 2021 and Albert Astals Cid committed May 02, 2021

When the ioctl() functions is executed correctly, the value of buffSize may be 0.
In this situation, there is no need to execute the following code.
This modification can solve two benefits:
1. The readFromInotify function runs frequently, and this modification can improve the
efficiency of the program.
2. When the buffSize is equal to 0, "read(inotifyFd, buffer.data(), buffSize)" function will
be stuck.(I have encountered this kind of problem)

Pick-to: 5.15 6.0 6.1
Change-Id: I9f85491ec91e336b4a1bec5c99b911835c5c06a5
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit bb8fc324)