bitbake.conf: remove 'extend_recipe_sysroot' from BB_HASHEXCLUDE_COMMON

bitbake.conf: remove 'extend_recipe_sysroot' from BB_HASHEXCLUDE_COMMON

'extend_recipe_sysroot' can and should be handled just like any other
function. Fine grained use of 'vardepsexclude' is capable of achieving
the same effect as ingoring 'extend_recipe_sysroot' on the base hash
level, but with a better visibility, and is a more uniform approach.

Signed-off-by: Adam Blank <adam.blank.g@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>