Module getauxvalCopy item path

Read auxv entries one at a time via getauxval.

Because the underlying getauxval C function is weakly linked, and only available on Linux, access to it is done via the trait Getauxval to provide some indirection. On target_os="linux", the struct NativeGetauxval will be available, and that will call through to getauxval if it is available and return an appropriate error if it is not. That means it should be safe to try it if you’re not sure your glibc has the function, etc.

On all OSs, if you want a no-op sort of implementation (for use on non-Linux OSs, etc), you can use NotAvailableGetauxval. It (surprise!) always returns the error that indicates that getauxval function was not found. Of course, you can also use write your own stub implementation of the trait for testing.