MinGW GCC 8.1.0, Windows 10 64-bit

Qt5.15.16

SET PATH=C:\Qt\Tools\mingw810_64\bin;C:\BUILD\qt-everywhere-src-5.15.16\qtbase\bin;%PATH%

 ..\qt-everywhere-src-5.15.16\configure.bat -release -prefix "C:\Qt\5.15.16\mingw81_64" -opensource -confirm-license -silent -make libs -nomake examples -nomake tests -make tools -skip qtwebengine -platform win32-g++ -opengl desktop -openssl-runtime OPENSSL_PREFIX="C:\Qt\Tools\OpenSSLv3\Win_x64" 
 
 mingw32-make
 mingw32-make install