recipetool: create: add basic support for extracting dependencies from cmake

recipetool: create: add basic support for extracting dependencies from cmake

Add support for extracting dependencies from CMakeLists.txt. There's
still a bunch of things missing that are outside the scope of OE-Core
and we still lack a proper extension mechanism, but this is a good
start.

This also adds an oe-selftest test to exercise the new code a bit.

Implements [YOCTO #7635].

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>