buildtools-tarball: Change the way the SDK is sanitized

buildtools-tarball: Change the way the SDK is sanitized

The previous method of shrinking down the scale of the environment-setup
file would not work properly when the target is configured with multilibs.

In addition, the configured machine name and similar settings could leak
into the SDK naming.  This was resolved by clearing the SDK generated
files and generating our own custom files.

Note, the name of the environment-setup now is suffixed with the SDK_SYS.

(From OE-Core rev: 778cd8d2110ef2db5ff4ae4f0b55c52a8f1ea334)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>