Executables that don't export a public API should not emit a
swiftmodule, but the swift modulename is observable from within the
program, so we should still set the module name on executable builds.
Fixes: #25710
The `-static` is important for the emission of the module as it is
serialized into the swiftmodule which then is used by the Swift frontend
to decide how to link to the symbol (via the GOT or not, or the IAT on
Windows). This repairs building static libraries with Swift on Windows.