osdep.h has a few things which are really compiler specific;
move them to compiler.h, and include compiler.h from osdep.h.
Backports commit 4912086865083a008f4fb73173fd0ddf2206c4d9 from qemu
Support for Cortex-M ARM CPU already exists in Qemu. This patch just
exposes a "cortex-m3" CPU.
"uc_open(UC_ARCH_ARM, UC_MODE_THUMB | UC_MODE_MCLASS, &uc);"
Instantiates a CPU with this feature on.
Signed-off-by: Lucian Cojocar <lucian@cojocar.com>