cmake: update common Zephyr build settings to use zephyr_get()

Fixes: #40389

This commit aligns the use of the following Zephyr build variables:
- CONF_FILE
- DTC_OVERLAY_FILE
- OVERLAY_CONFIG
- WEST_DIR
- ZEPHYR_BOARD_ALIASES
- ZEPHYR_EXTRA_MODULES
- ZEPHYR_MODULES

so that they can be set in same manner and with same order of
preference.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

cmake/flash/CMakeLists.txt

@@ -128,10 +128,7 @@ if(RUNNERS)
   create_runners_yaml(${RUNNERS})
 endif()
 
-if(DEFINED ENV{WEST_DIR} AND NOT WEST_DIR)
-  set(WEST_DIR $ENV{WEST_DIR})
-endif(DEFINED ENV{WEST_DIR} AND NOT WEST_DIR)
-
+zephyr_get(WEST_DIR)
 if(WEST_DIR)
   set(WEST "PYTHONPATH=${WEST_DIR}/src" "${PYTHON_EXECUTABLE};${WEST_DIR}/src/west/app/main.py;--zephyr-base=${ZEPHYR_BASE} ")
 endif()

cmake/modules/boards.cmake

@@ -64,8 +64,9 @@ if(NOT (REVISION_SEPARATOR_INDEX EQUAL -1))
   string(SUBSTRING ${BOARD} 0 ${REVISION_SEPARATOR_INDEX} BOARD)
 endif()
 
-if(DEFINED ENV{ZEPHYR_BOARD_ALIASES})
-  include($ENV{ZEPHYR_BOARD_ALIASES})
+zephyr_get(ZEPHYR_BOARD_ALIASES)
+if(DEFINED ZEPHYR_BOARD_ALIASES)
+  include(${ZEPHYR_BOARD_ALIASES})
   if(${BOARD}_BOARD_ALIAS)
     set(BOARD_ALIAS ${BOARD} CACHE STRING "Board alias, provided by user")
     set(BOARD ${${BOARD}_BOARD_ALIAS})

cmake/modules/configuration_files.cmake

@@ -35,6 +35,7 @@ else()
   set(APPLICATION_CONFIG_DIR ${APPLICATION_SOURCE_DIR})
 endif()
 
+zephyr_get(CONF_FILE)
 if(DEFINED CONF_FILE)
   # This ensures that CACHE{CONF_FILE} will be set correctly to current scope
   # variable CONF_FILE. An already current scope variable will stay the same.
@@ -62,9 +63,6 @@ elseif(CACHED_CONF_FILE)
   # That value has precedence over anything else than a new
   # `cmake -DCONF_FILE=<file>` invocation.
   set(CONF_FILE ${CACHED_CONF_FILE})
-elseif(DEFINED ENV{CONF_FILE})
-  set(CONF_FILE $ENV{CONF_FILE})
-
 elseif(EXISTS   ${APPLICATION_CONFIG_DIR}/prj_${BOARD}.conf)
   set(CONF_FILE ${APPLICATION_CONFIG_DIR}/prj_${BOARD}.conf)
 
@@ -91,6 +89,7 @@ zephyr_file(CONF_FILES ${APPLICATION_CONFIG_DIR}/boards DTS APP_BOARD_DTS)
 # The CONF_FILE variable is now set to its final value.
 zephyr_boilerplate_watch(CONF_FILE)
 
+zephyr_get(DTC_OVERLAY_FILE)
 if(DTC_OVERLAY_FILE)
   # DTC_OVERLAY_FILE has either been specified on the cmake CLI or is already
   # in the CMakeCache.txt.

cmake/modules/kconfig.cmake

@@ -72,6 +72,7 @@ if(CONF_FILE)
 string(REPLACE " " ";" CONF_FILE_AS_LIST "${CONF_FILE}")
 endif()
 
+zephyr_get(OVERLAY_CONFIG)
 if(OVERLAY_CONFIG)
   string(REPLACE " " ";" OVERLAY_CONFIG_AS_LIST "${OVERLAY_CONFIG}")
 endif()

cmake/modules/zephyr_module.cmake

@@ -31,18 +31,12 @@ include(python)
 # Settings used by Zephyr module but where systems may define an alternative value.
 set_ifndef(KCONFIG_BINARY_DIR ${CMAKE_BINARY_DIR}/Kconfig)
 
-if(ZEPHYR_EXTRA_MODULES)
-  # ZEPHYR_EXTRA_MODULES has either been specified on the cmake CLI or is
-  # already in the CMakeCache.txt. This has precedence over the environment
-  # variable ZEPHYR_EXTRA_MODULES
-elseif(DEFINED ENV{ZEPHYR_EXTRA_MODULES})
-  set(ZEPHYR_EXTRA_MODULES $ENV{ZEPHYR_EXTRA_MODULES})
-endif()
-
+zephyr_get(ZEPHYR_MODULES)
 if(ZEPHYR_MODULES)
   set(ZEPHYR_MODULES_ARG "--modules" ${ZEPHYR_MODULES})
 endif()
 
+zephyr_get(ZEPHYR_EXTRA_MODULES)
 if(ZEPHYR_EXTRA_MODULES)
   set(ZEPHYR_EXTRA_MODULES_ARG "--extra-modules" ${ZEPHYR_EXTRA_MODULES})
 endif()