Currently, providers are set on a global config basis. This change allows
for a select set of providers configured in BB_RECIPE_VIRTUAL_PROVIDERS to
be selected on a per recipe basis. This would allow for the selection of
virtual/cross-cc as gcc or clang for example in OE-Core.
DEPENDS and task flag [depends] values are processed.
(Bitbake rev: fb119c7888ae8a749aa824f8c51780176af077f9)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>