This removes the need for using NSS Build Tools on windows.
It also removes the nees to build nss for the build system while cross
compiling.

Change-Id: I13c9fdb575223f2940d3e4eda00e77ba9158f2b7
Reviewed-on: https://gerrit.libreoffice.org/1534Reviewed-by: Tor Lillqvist <tml@iki.fi>
Tested-by: Tor Lillqvist <tml@iki.fi>