fixup "vbox: don't run shared folder test on qemu"

@alex-ab is this wording okay for you (and the checker mimic)?
hw: map a dataspace in core according to its flags

Thereby removing obsolete quirk for uncached CPU state dataspace
in VM session.

Fixes #1198
hw_imx31: fix compilation error in timer.h

fix #1200
hw: core as library

The build config for core is now provided through libraries to enable
implicit config composition through specifiers and thereby avoid
consideration of inappropriate targets.

fix #1199