make $$join() implementation qmake-compliant
make $$join() implementation qmake-compliant

Task-number: QTCREATORBUG-6441

Change-Id: I1d18c81f76cda71654a85c23b7b53b4aae0d51c6
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@nokia.com>
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@nokia.com>

KDE/android-qt-creator,KDAB/KDAB-Creator,ostash/qt-creator-i18n-uk,danimo/qt-creator,syntheticpp/qt-creator,malikcjm/qtcreator,maui-packages/qt-creator,colede/qtcreator,Distrotech/qtcreator,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,kuba1/qtcreator,farseerri/git_code,kuba1/qtcreator,ostash/qt-creator-i18n-uk,richardmg/qtcreator,colede/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,martyone/sailfish-qtcreator,syntheticpp/qt-creator,farseerri/git_code,hdweiss/qt-creator-visualizer,azat/qtcreator,kuba1/qtcreator,ostash/qt-creator-i18n-uk,KDAB/KDAB-Creator,AltarBeastiful/qt-creator,colede/qtcreator,farseerri/git_code,darksylinc/qt-creator,martyone/sailfish-qtcreator,jonnor/qt-creator,danimo/qt-creator,jonnor/qt-creator,maui-packages/qt-creator,kuba1/qtcreator,bakaiadam/collaborative_qt_creator,martyone/sailfish-qtcreator,danimo/qt-creator,azat/qtcreator,farseerri/git_code,amyvmiwei/qt-creator,xianian/qt-creator,ostash/qt-creator-i18n-uk,hdweiss/qt-creator-visualizer,xianian/qt-creator,danimo/qt-creator,syntheticpp/qt-creator,richardmg/qtcreator,darksylinc/qt-creator,bakaiadam/collaborative_qt_creator,hdweiss/qt-creator-visualizer,xianian/qt-creator,jonnor/qt-creator,amyvmiwei/qt-creator,darksylinc/qt-creator,KDE/android-qt-creator,Distrotech/qtcreator,martyone/sailfish-qtcreator,kuba1/qtcreator,malikcjm/qtcreator,omniacreator/qtcreator,amyvmiwei/qt-creator,amyvmiwei/qt-creator,darksylinc/qt-creator,kuba1/qtcreator,xianian/qt-creator,kuba1/qtcreator,darksylinc/qt-creator,richardmg/qtcreator,Distrotech/qtcreator,AltarBeastiful/qt-creator,omniacreator/qtcreator,xianian/qt-creator,maui-packages/qt-creator,xianian/qt-creator,duythanhphan/qt-creator,duythanhphan/qt-creator,xianian/qt-creator,omniacreator/qtcreator,malikcjm/qtcreator,hdweiss/qt-creator-visualizer,ostash/qt-creator-i18n-uk,darksylinc/qt-creator,bakaiadam/collaborative_qt_creator,jonnor/qt-creator,ostash/qt-creator-i18n-uk,KDE/android-qt-creator,syntheticpp/qt-creator,jonnor/qt-creator,danimo/qt-creator,farseerri/git_code,omniacreator/qtcreator,malikcjm/qtcreator,AltarBeastiful/qt-creator,xianian/qt-creator,malikcjm/qtcreator,jonnor/qt-creator,omniacreator/qtcreator,Distrotech/qtcreator,farseerri/git_code,Distrotech/qtcreator,amyvmiwei/qt-creator,duythanhphan/qt-creator,bakaiadam/collaborative_qt_creator,duythanhphan/qt-creator,richardmg/qtcreator,amyvmiwei/qt-creator,martyone/sailfish-qtcreator,darksylinc/qt-creator,colede/qtcreator,duythanhphan/qt-creator,darksylinc/qt-creator,KDE/android-qt-creator,azat/qtcreator,farseerri/git_code,KDE/android-qt-creator,danimo/qt-creator,maui-packages/qt-creator,maui-packages/qt-creator,bakaiadam/collaborative_qt_creator,omniacreator/qtcreator,Distrotech/qtcreator,bakaiadam/collaborative_qt_creator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,duythanhphan/qt-creator,azat/qtcreator,danimo/qt-creator,xianian/qt-creator,syntheticpp/qt-creator,azat/qtcreator,farseerri/git_code,martyone/sailfish-qtcreator,syntheticpp/qt-creator,duythanhphan/qt-creator,KDE/android-qt-creator,hdweiss/qt-creator-visualizer,KDE/android-qt-creator,colede/qtcreator,maui-packages/qt-creator,AltarBeastiful/qt-creator,omniacreator/qtcreator,bakaiadam/collaborative_qt_creator,KDAB/KDAB-Creator,martyone/sailfish-qtcreator,KDAB/KDAB-Creator,richardmg/qtcreator,KDAB/KDAB-Creator,hdweiss/qt-creator-visualizer,kuba1/qtcreator,maui-packages/qt-creator,azat/qtcreator,AltarBeastiful/qt-creator,colede/qtcreator,danimo/qt-creator,ostash/qt-creator-i18n-uk,amyvmiwei/qt-creator,richardmg/qtcreator,KDAB/KDAB-Creator,KDE/android-qt-creator,colede/qtcreator,malikcjm/qtcreator,malikcjm/qtcreator,AltarBeastiful/qt-creator,richardmg/qtcreator,danimo/qt-creator,AltarBeastiful/qt-creator