[be-script] add option to run zypper refresh for MerSDK

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[readme] added a link to wget

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[buildqtc] added keep template option to windows build too

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[be-script] clean up the correct files

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[buildqtc] windows - clean installdir in bat

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[buildqtc] create a workdir for the build and use INSTALLER_ARCHIVE

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>