Fix QStringBuilder taking reference to temporary due to auto
Summary:
Compiler decides for "auto" type result to use QStringBuilder, though the
expression passed to it includes a temporary QString result from a
QStringList::join() result. Which then is dropped after the assignement, due
to getting out of scope.
BUG: 394055
Reviewers: KDevelop, shashwatdixit, mwolff, kfunk
Reviewed By: KDevelop, kfunk
Subscribers: kfunk, kdevelop-devel
Tags: KDevelop
Differential Revision: https://phabricator.kde.org/D14235