license.bbclass: fix warnings when run in unprivileged "container" env

license.bbclass: fix warnings when run in unprivileged "container" env

An unprivileged "container" environment like this[1] doesn't have root
account (uid 0) which causes tons of "Invalid argument" warnings:

  $ bitbake ...
  ...
  WARNING: Could not copy license file [src] to [dest]: [Errno 22] Invalid argument: '[src]'
  WARNING: Could not copy license file [src] to [dest]: [Errno 22] Invalid argument: '[src]'
  WARNING: Could not copy license file [src] to [dest]: [Errno 22] Invalid argument: '[src]'
  ...

Fix it by handling EINVAL similar to existing handling of EPERM (which
was added for when not running under pseudo).

[1]: The real environemnt is buildFHSUserEnv from NixOS/nixpkgs, but a
  demonstration of the issue can be done like this:

    $ touch f
    $ unshare --user --mount chown 0:0 f
    chown: changing ownership of ‘f’: Invalid argument

Signed-off-by: Bjørn Forsman <bjorn.forsman@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>