Some upstream projects are employing the buildtype parameter so users
can create, say, "production" versus "debug" builds. Therefore create a
configurable parameter so recipes/users can tweak it.
(From OE-Core rev: 5b12211ef7856bedafd356f6b7a03add46eca6c7)
Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>