Log Message:
qt5: updated to 5.12.0

Just in time for the end of the year, we have released Qt 5.12 LTS today. This \ 
is a long-term-supported (LTS) release that we will support for 3 years to come. \ 
We have had a strong focus on quality and fixed more than 2000 bugs since the \ 
last Qt LTS version, Qt 5.9.7 – make that over 5000 bugfixes since Qt 5.6.3. \ 
Of course, this is only the start, and we will work hard on continuously \ 
improving the quality of Qt 5.12 in upcoming patches