debug/gdb: fix canadian-cross in case of static cross gdb

Building the cross-gdb shoud be done using the host compiler,
not the native compiler.

Reported-by: Per Arnold Blaasmo <per-arnold.blaasmo@atmel.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 reporter_name="Yann Diorcet <diorcet.yann@gmail.com>"

 reporter_url=""

 reporter_comment="Config to build cross-compiler with mingw as kernel type for

 32 bits Windows target"