linux-user: introduce parameters to generate syscall_nr.h

linux-user: introduce parameters to generate syscall_nr.h

This will be used when we'll import syscall.tbl from the kernel

Add a script to remove all the dependencies to syscall_nr.h
that point to source directory and not to the build directory.
The list of arch will be update while the generated files are added.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20200310103403.3284090-2-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>