Makefile: remove a whitespace error

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Makefile: break out LDSCRIPT variable

We are going to want to use this value separately in the next commit.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
app-tools: Provide rumpxen-app-* helpers

Provide:

 * A GCC wrapper which allows a naive Makefile to compile and link an
   "executable" to generate a rump kernel image.  This uses:

 * A GCC specs file.  This provides the right "system" include
   directories - that is, the headers for the rump kernel application
   environment.  It also uses:

 * A stunt wrapper for "ld".  Building a minios-based Xen image needs
   two runs of ld.  This ld wrapper parses and categorises its
   arguments and runs the two appropriate link steps.

 * A pair of simple wrapper scripts for configure and make, which set
   CC and pass the --host= option.

With these changes, and a suitably modified xen.git, we can run
configure and build a relevant subset of the Xen management libraries
and tools.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Makefile etc.: Use -no-integrated-cpp

I have found that GCC 4.7.2 (Debian i386 4.7.2-5) sometimes misreports
errors relating to broken #includes when the integrated cpp is in use.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>