gdb-cross-canadian: build gdb with python support

* python support is needed for providing finer scripting control
in gdb, and for remote controling gdb for example from qtcreator
* gdb/configure tries to autodetect python using python executable
with --includes --ldflags --exec-prefix to get the right flags
As it's difficult to achieve in OE's context, we generate a
script which will return the right values and make gdb's build
system happy. This idea was taken from the following article :
http://www.mentby.com/doug-evans-2/python-enabled-gdb-on-windows-and-relocation.html


* tested using angstrom & armv7/armv5 targets & qtcreator 201005 & 2.4.0

Signed-off-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>