cmake: store a variable reference in cache for TF-M signing code

This commit stores a partition manager variable reference in the CMake
cache, so that sysbuild can update with correct value after partition
manager has completed.

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

cmake/sysbuild/tfm_signing.cmake

@@ -87,9 +87,8 @@ function(zephyr_mcuboot_tasks)
 #endforeach()
 
 #  set(west_sign imgtool sign --version 0.0.0+0 --align 4 --slot-size 262144 --pad-header --header-size 0x200)
-  string(TOUPPER "${DEFAULT_IMAGE}" application_uppercase)
-#  set(west_sign imgtool sign --version 0.0.0+0 --align 4 --slot-size $<TARGET_PROPERTY:partition_manager,PM_${application_uppercase}_SIZE> --pad-header --header-size ${SB_CONFIG_PM_MCUBOOT_PAD})
-  set(west_sign imgtool sign --version ${CONFIG_MCUBOOT_IMGTOOL_SIGN_VERSION} --align 4 --slot-size 0xa8000) #--pad-header --header-size ${SB_CONFIG_PM_MCUBOOT_PAD})
+  set(west_sign imgtool sign --version 0.0.0+0 --align 4 --slot-size @PM_APP_SIZE@ CACHE STRING "west sign command")
+#  set(west_sign imgtool sign --version ${CONFIG_MCUBOOT_IMGTOOL_SIGN_VERSION} --align 4 --slot-size 0xa8000) #--pad-header --header-size ${SB_CONFIG_PM_MCUBOOT_PAD})
 
   # Arguments to imgtool.
   if(NOT CONFIG_MCUBOOT_EXTRA_IMGTOOL_ARGS STREQUAL "")

sysbuild/CMakeLists.txt

@@ -200,6 +200,9 @@ include_packaging()
     include(${ZEPHYR_NRF_MODULE_DIR}/cmake/sysbuild/partition_manager.cmake OPTIONAL)
   endif()
 
+  # temp hack, load the specifically needed PM setting into a CMake current scope var.
+  get_property(PM_APP_SIZE TARGET partition_manager PROPERTY PM_APP_SIZE)
+  get_property(PM_MCUBOOT_PAD TARGET partition_manager PROPERTY PM_MCUBOOT_PAD)
   foreach(image ${IMAGES})
     configure_cache(IMAGE ${image})
   endforeach()