[nrf fromtree] sysbuild: add support for APPLICATION_CONFIG_DIR in sysbuild

APPLICATION_CONFIG_DIR is supported in Zephyr and allows to adjust the
location from which prj.conf and friends are picked up.

This also works for images when using sysbuild, however sysbuild itself
ignores the value of APPLICATION_CONFIG_DIR, meaning that sysbuild only
accepts sysbuild.conf located directly in the sample folder.

Extend sysbuild to support APPLICATION_CONFIG_DIR so sysbuild follows
regular Zephyr CMake behavior.

Introduce SB_APPLICATION_CONFIG_DIR to allow changing the location
for sysbuild only, without propagating the value to images.

Signed-off-by: Torsten Rasmussen <[email protected]>
(cherry picked from commit 2b427f1)
(cherry picked from commit 6be1849)

Author: tejlmand

share/sysbuild/cmake/modules/sysbuild_kconfig.cmake

@@ -13,13 +13,37 @@ set(EXTRA_KCONFIG_TARGET_COMMAND_FOR_sysbuild_guiconfig
 set(KCONFIG_TARGETS sysbuild_menuconfig sysbuild_guiconfig)
 list(TRANSFORM EXTRA_KCONFIG_TARGETS PREPEND "sysbuild_")
 
+if(DEFINED APPLICATION_CONFIG_DIR AND NOT DEFINED CACHE{APPLICATION_CONFIG_DIR})
+  set(APPLICATION_CONFIG_DIR "${APPLICATION_CONFIG_DIR}" CACHE INTERNAL "Application config dir")
+elseif(DEFINED CACHE{APPLICATION_CONFIG_DIR} AND
+       NOT (APPLICATION_CONFIG_DIR STREQUAL "$CACHE{APPLICATION_CONFIG_DIR}"))
+  message(WARNING
+          "Sysbuild scoped APPLICATION_CONFIG_DIR and cached APPLICATION_CONFIG_DIR differs.\n"
+          "Setting value used internally by Sysbuild (sysbuild scoped):\n"
+	  " - ${APPLICATION_CONFIG_DIR}\n"
+	  "Setting value used by images (cached):\n"
+	  " - $CACHE{APPLICATION_CONFIG_DIR}\n"
+  )
+endif()
+
+# If there is a dedicated SB_APPLICATION_CONFIG_DIR, then create a local
+# scoped APPLICATION_CONFIG_DIR hiding any cache variant.
+# The cache setting is the setting passed to sysbuild image cache files
+if(DEFINED SB_APPLICATION_CONFIG_DIR)
+  set(APPLICATION_CONFIG_DIR ${SB_APPLICATION_CONFIG_DIR})
+elseif(NOT DEFINED APPLICATION_CONFIG_DIR)
+  get_filename_component(APP_DIR  ${APP_DIR} ABSOLUTE)
+  set(APPLICATION_CONFIG_DIR ${APP_DIR})
+endif()
+string(CONFIGURE ${APPLICATION_CONFIG_DIR} APPLICATION_CONFIG_DIR)
+
 if(DEFINED SB_CONF_FILE)
   # SB_CONF_FILE already set so nothing to do.
 elseif(DEFINED ENV{SB_CONF_FILE})
   set(SB_CONF_FILE $ENV{SB_CONF_FILE})
 else()
   # sysbuild.conf is an optional file, because sysbuild is an opt-in feature.
-  zephyr_file(CONF_FILES ${APP_DIR} KCONF SB_CONF_FILE NAMES "sysbuild.conf" SUFFIX ${FILE_SUFFIX})
+  zephyr_file(CONF_FILES ${APPLICATION_CONFIG_DIR} KCONF SB_CONF_FILE NAMES "sysbuild.conf" SUFFIX ${FILE_SUFFIX})
 endif()
 
 if(NOT DEFINED SB_EXTRA_CONF_FILE AND DEFINED SB_OVERLAY_CONFIG)