Define SOCI_DEFAULT_CMAKE_OPTIONS once and use it in almost all builds
instead of repeating the same options many times everywhere.
For the remaining build (Valgrind) still reuse a couple of options which
it has in common with the other ones.
This doesn't work currently because Oracle installation requires access
to secret environment variables which are unavailable for the PR builds
for the security purposes, so skip trying to do it to at least avoid
failing all PR builds.
Closes#584.
Vadim Zeitlin