build: fix race when creating the cpu_map.xml symlink

build: fix race when creating the cpu_map.xml symlink

In some circumstances where the build tree differs from the source,
libvirt's compile will try to create the symlink for cpu_map.xml before
creating the directory $(abs_builddir)/cpu:

'src/cpu/cpu_map.xml': No such file or directory'

Do not create the symlink, it is no longer needed after
commit e562e82f
    Load CPU map from builddir when run uninstalled

Signed-off-by: Amy Fong <amy.fong@windriver.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>