Config.mk: commented-out CONFIG_QEMU example now uses `pwd`/$(XEN_ROOT)

If you actually set it to a relative path, the qemu build breaks.
So this commented-out rune (an example) should arrange to be absolute.

Unfortunately XEN_ROOT is itself relative so the previous attempt to
fix this (22772:654563af359f) didn't work. So use `pwd`.

Tested-by: M A Young <m.a.young@durham.ac.uk>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

     1.1 --- a/Config.mk	Thu Jan 27 19:03:42 2011 +0000
     1.2 +++ b/Config.mk	Thu Jan 27 19:42:40 2011 +0000
     1.3 @@ -182,7 +182,7 @@ endif
     1.4  
     1.5  # Specify which qemu-dm to use. This may be `ioemu' to use the old
     1.6  # Mercurial in-tree version, or a local directory, or a git URL.
     1.7 -# CONFIG_QEMU ?= $(XEN_ROOT)/../qemu-xen.git
     1.8 +# CONFIG_QEMU ?= `pwd`/$(XEN_ROOT)/../qemu-xen.git
     1.9  CONFIG_QEMU ?= $(QEMU_REMOTE)
    1.10  
    1.11  QEMU_TAG := xen-4.1.0-rc2