samba: backport patches for cross-compiling

* Adds a new mode for samba cross-compiling:

  When both --cross-answers and --cross-execute are set, this means:
  - Use cross-answers
  - If answer is unknown, then instead of adding UNKNOWN to the cross-answers
    file and failing configure, the new mode runs cross-execute to determine the
    answer and adds that to the cross-answers file.

* And some fixes and improvements for cross-compiling.

Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>