Upgrade `cmake_minimum_required` from `(VERSION 2.8)` to `(VERSION 2.9)` to
yield the warning:
"Compatibility with CMake < 2.8.12 will be removed from a future version of CMake"
Add "-Wno-unused" for CMAKE_CXX_FLAGS to yield the compilation warnings
when build LLVM JIT.
Fix the link error when code coverage is enabled.
Apply clang-format for C source files in folder core/app-mgr,
core/app-framework, and test-tools.
And rename folder component_test to component-test, update
zephyr build document.
Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>
