build system: Initial cmake support, work in progress

examples/get-started/hello_world/CMakeLists.txt

@@ -0,0 +1,12 @@
+# The following four lines of boilerplate have to be in your project's CMakeLists
+# in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.5)
+set(CMAKE_TOOLCHAIN_FILE $ENV{IDF_PATH}/toolchain.cmake)
+project(idf_project ASM C CXX)
+
+include($ENV{IDF_PATH}/idf.cmake)
+
+add_executable(hello_world.elf
+  main/hello_world_main.c)
+
+target_link_libraries(hello_world.elf ${COMPONENT_LIBRARIES})