tools/fuzz/x86_instruction_emulator: rework makefile

tools/fuzz/x86_instruction_emulator: rework makefile

Rework dependencies of all objects. We don't need to add dependencies
for headers that $(CC) is capable of generating, we only need to
include $(DEPS_INCLUDE). Some dependencies are still needed so make
knows to generate symlinks for them.

We remove the use of "vpath" for cpuid.c. While it works fine for now,
when we will convert this makefile to subdirmk, vpath will not be
usable. Also, "-iquote" is now needed to build "cpuid.o".

Replace "-I." by "-iquote .", so it applies to double-quote includes
only.

Rather than checking if a symlink exist, always regenerate the
symlink. So if the source tree changed location, the symlink is
updated.

Since we are creating a new .gitignore for the symlink, also move the
entry to it.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Jan Beulich <jbeulich@suse.com>