populate_sdk_ext: Avoid copying and producing .pyc files

Since pyc cache files are really system specific, no real reason to copy or
generate them during the eSDK build process.  Also generating them has the
possibility of re-using inodes that pseudo may have been tracking, leading
a build failure.

Signed-off-by: Mark Hatle <mark.hatle@kernel.crashing.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>