qmake: use QString::replace() overloaded with QLatin1String

instead of QStringLiteral, QString, const char*.

Results: reduce .rodata, prevent re-creation of QString.

Change-Id: Ie2e3089974c42e6733457bbe58521bccd1da3a53
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>