Enable RandomizedBaseAddress (ASLR) on Windows with MSVC builds

Enable RandomizedBaseAddress (ASLR) on Windows with MSVC builds

This has as effect to add /DYNAMICBASE to the .dll and .exe files
generated by the builds, undoing 7f3e17b.  Note that ASLR was already
enabled in MinGW as we have never added --disable-dynamicbase there.

This change will ease a bit the integration of arm64 with MSVC, as ASLR
support is mandatory in this case.  So, thanks to this commit, we have
no need to make ASLR conditional depending on the architecture used for
the build.

Andres Freund has done a lot of testing with this option while working
on meson, without seeing /DYNAMICBASE as being a problem in the Windows
builds of the CI.  Personally, not supporting anything older than
Windows 10 on HEAD makes me feel safer about this change, as we have
seen ASLR with being a problem in process invocation particularly with
Windows 8 and server 2012 back in 2014, even if Windows 10 was not
really a thing back then.  45e004f is also something that can help in
making the process invocation more stable.  We are very early in the
development of Postgres 16, giving a lot of room to detect stability
issues if any.

Discussion: https://postgr.es/m/20220826012907.gjw3jdqdgsts5y65@awork3.anarazel.de