...instead of inconsitently having it depend on --enable-epm for some platforms
and having it always enabled on Windows.  Only Android and iOS are presumably
still special and build any installation sets in their specific modules and
outside instsetoo_native.

One consequence is that for a non-Windows --enable-online-update
--without-package-format build, instdir's version ini-file contains an
UpdateURL that ends in just "?pkgfmt=" without an actual format identifier.
However, checking whether the update feature would actually work is difficult
for most such developer builds, anyway.

Change-Id: If14fcf0b2e612499811e8a6e067a854bda612c42