Mitigate CVE-2019-1552 vulnerability in Qt

Customers might ship their Qt application with OpenSSL binaries that load configurations and extension DLLs from an insecure location:

https://www.openssl.org/news/secadv/20190730.txt

In order to protect Qt applications against such an attack vector, we should employ the following mechanism: If Qt loads a side-loaded set of OpenSSL libraries (that is, found next to the Qt DLLs), we override the OPENSSL_CONF environment variable to point to

QDir(QLibraryInfo::location(QLibraryInfo::Prefix)).absoluteFilePath(QT_CONFIGURE_SETTINGS_PATH)

This needs to be done before Qt's OpenSSL module executes the OPENSSL_add_all_algorithms_conf API call.