build: Add update-linux-vdso makefile rule

This is not ideal, since it requires all cross-compilers
to be present rather than a simple subset.  But since it
is only run manually, should be good enough for now.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed