Need newer gcc for x64->armv7 crosscompilation

In QtWebEngine for 6.5 we are hitting this internal compiler error https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102842

It should be solved in gcc 10.4, but we are using gcc 10.2. Note since we will probably use QtWebEngine 6.5 with Qt 6.2 LTS in half a year, the compiler should also be updated in the 6.2 lts branch.