[nrfconnect] Simplify CMake files (project-chip#4524)

* [nrfconnect] Simplify CMake files

Get rid of app.cmake file by leveraging Zephyr standard
mechanisms to:
* automatically link the app with CHIP libraries when
  CHIP is loaded as a Zephyr module.
* automatically pull a Device Tree overlay for a selected
  board into the project.

* Restyled by prettier-markdown

Co-authored-by: Restyled.io <commits@restyled.io>

Author: Damian-Nordic

config/nrfconnect/README.md

@@ -3,9 +3,8 @@
 This directory contains build scripts and common configuration files used by
 CHIP nRF Connect applications. It is structured as follows:
 
-| File/Folder   | Contents                                                                                                                                                       |
-| ------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| chip-gn       | GN project used to build selected CHIP libraries with the _nrfconnect_ platform integration layer                                                              |
-| chip-module   | CMake wrapper for the GN project defined in `chip-gn` directory, and other components that allow one to use CHIP as a Zephyr module                            |
-| app/app.cmake | Helper CMake module to be used by nRF Connect applications in this repository to inject `chip-module` into the Zephyr module list and load Zephyr build system |
-| app/\*.conf   | Common and optional Kconfig configuration files that can be used in nRF Connect applications                                                                   |
+| File/Folder | Contents                                                                                                                            |
+| ----------- | ----------------------------------------------------------------------------------------------------------------------------------- |
+| chip-gn     | GN project used to build selected CHIP libraries with the _nrfconnect_ platform integration layer                                   |
+| chip-module | CMake wrapper for the GN project defined in `chip-gn` directory, and other components that allow one to use CHIP as a Zephyr module |
+| app         | Common and optional Kconfig configuration files that can be used in nRF Connect applications                                        |

config/nrfconnect/app/app.cmake

@@ -88,4 +88,11 @@ config CHIP_NFC_COMMISSIONING
 	help
 	  Enables NFC commissioning by sharing onboarding payload in NFC tag.
 
+config APP_LINK_WITH_CHIP
+	bool "Link 'app' with Connected Home over IP"
+	default y
+	help
+	  Add Connected Home over IP header files to the 'app' include path
+	  and link the 'app' with Connected Home over IP libraries.
+
 endif

config/nrfconnect/chip-module/Kconfig

@@ -21,7 +21,9 @@ get_filename_component(LIGHTING_COMMON ${CHIP_ROOT}/examples/lighting-app/lighti
 
 set(CONF_FILE ${CHIP_ROOT}/config/nrfconnect/app/sample-defaults.conf prj.conf)
 
-include(${CHIP_ROOT}/config/nrfconnect/app/app.cmake)
+# Load NCS/Zephyr build system
+list(APPEND ZEPHYR_EXTRA_MODULES ${CHIP_ROOT}/config/nrfconnect/chip-module)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
 
 project(chip-nrf52840-lighting-example)
 

examples/lighting-app/nrfconnect/CMakeLists.txt

@@ -21,7 +21,9 @@ get_filename_component(LOCK_COMMON ${CHIP_ROOT}/examples/lock-app/lock-common RE
 
 set(CONF_FILE ${CHIP_ROOT}/config/nrfconnect/app/sample-defaults.conf prj.conf)
 
-include(${CHIP_ROOT}/config/nrfconnect/app/app.cmake)
+# Load NCS/Zephyr build system
+list(APPEND ZEPHYR_EXTRA_MODULES ${CHIP_ROOT}/config/nrfconnect/chip-module)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
 
 project(chip-nrf52840-lock-example)
 

examples/lighting-app/nrfconnect/dts.overlay examples/lighting-app/nrfconnect/boards/nrf52840dk_nrf52840.overlay

@@ -23,7 +23,9 @@ if(${BOARD} STREQUAL "nrf52840dongle_nrf52840")
     list(INSERT OVERLAY_CONFIG 0 ${CHIP_ROOT}/config/nrfconnect/app/overlay-usb_support.conf)
 endif()
 
-include(${CHIP_ROOT}/config/nrfconnect/app/app.cmake)
+# Load NCS/Zephyr build system
+list(APPEND ZEPHYR_EXTRA_MODULES ${CHIP_ROOT}/config/nrfconnect/chip-module)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
 
 project(chip-nrf52840-pigweed-example)
 

examples/lock-app/nrfconnect/CMakeLists.txt

@@ -20,7 +20,9 @@ get_filename_component(APP_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/.. REALPATH)
 
 set(CONF_FILE ${CHIP_ROOT}/config/nrfconnect/app/sample-defaults.conf prj.conf)
 
-include(${CHIP_ROOT}/config/nrfconnect/app/app.cmake)
+# Load NCS/Zephyr build system
+list(APPEND ZEPHYR_EXTRA_MODULES ${CHIP_ROOT}/config/nrfconnect/chip-module)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
 
 project(chip-nrf52840-shell-example)
 

examples/lock-app/nrfconnect/dts.overlay examples/lock-app/nrfconnect/boards/nrf52840dk_nrf52840.overlay

@@ -73,7 +73,9 @@ set(CHIP_LIBRARIES
     ${CHIP_TESTS}
 )
 
-include(${CHIP_ROOT}/config/nrfconnect/app/app.cmake)
+# Load NCS/Zephyr build system
+list(APPEND ZEPHYR_EXTRA_MODULES ${CHIP_ROOT}/config/nrfconnect/chip-module)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
 
 # ==================================================
 # Build 'all tests' runner