autotools/siteinfo: Tweak CONFIG_SITE handling for determism/races
As things stand there are multiple races in the CONFIG_SITE handling
where checksums can change depending on whether site directories
exist or not when parsing happens. This is bad.
Secondly, there is a build race that occurs if you build virtuals
in parallel with the "main" recipe, since the main recipe is parsed
when the virtual is (since it sets variables like BBCLASSEXTEND)
and with the current code, it may look for files and directories
which could be created/destroyed which the loop is executing. This
is also bad.
The aclocal-copy directory should only ever be accessed by the call
from autotools.bbclass. This changes the parameter name to make it
clear and ensures all callers have the right usage, neatly avoiding
all the problems above. Also added better comments.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
