qmake: fix file id mapping lifetime management

turns out that flushing the ids together with the ProFile cache was an
abysmal idea, as the latter expires after a few seconds after loading
the project, while references to the ProFiles (and thus the underlying
file ids) are kept for as long as the project stays loaded. the early
flush would cause re-use of the file ids, which would wreak all kinds of
havoc when re-loading projects.

instead, ref-count the vfs class based on its instances.

amends 60245e55d7.

Task-number: QTCREATORBUG-20113
Change-Id: I7382a71af4d6a991156c05719deae9fb1e4fb278
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

0 files changed, 0 insertions, 0 deletions