cmake: runners dependencies cleanup

This commit renames `FLASH_DEPS` to `RUNNERS_DEPS`.
The current name `FLASH_DEPS` is misleading in the sense that this
depency is added to all runner targets, flash, debug, debugserver,
attach, and not only the flash runners.

Therefore this is now named `RUNNERS_DEPS` instead.

Similar, zephyr_property_target now contains the property
FLASH_DEPENDENCIES, DEBUG_DEPENDENCIES, and so on, so that additional
dependencies can be added for each runner.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7709cbc..8f4d078 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1344,7 +1344,7 @@
     )
 
   add_custom_target(mergehex ALL DEPENDS ${MERGED_HEX_NAME})
-  list(APPEND FLASH_DEPS mergehex)
+  list(APPEND RUNNERS_DEPS mergehex)
 
   message(VERBOSE "Merging hex files: ${HEX_FILES_TO_MERGE}")
 endif()
diff --git a/cmake/flash/CMakeLists.txt b/cmake/flash/CMakeLists.txt
index cec49f0..aaa0641 100644
--- a/cmake/flash/CMakeLists.txt
+++ b/cmake/flash/CMakeLists.txt
@@ -179,8 +179,9 @@
   elseif(target STREQUAL attach)
     set(comment "Debugging ${BOARD}")
   endif()
+  string(TOUPPER ${target} TARGET_UPPER)
 
-  list(APPEND FLASH_DEPS ${logical_target_for_zephyr_elf})
+  list(APPEND RUNNERS_DEPS ${logical_target_for_zephyr_elf})
 
   # Enable verbose output, if requested.
   if(CMAKE_VERBOSE_MAKEFILE)
@@ -198,8 +199,8 @@
       ${RUNNER_VERBOSE}
       ${target}
       --skip-rebuild
-      DEPENDS ${FLASH_DEPS}
-              $<TARGET_PROPERTY:zephyr_property_target,FLASH_DEPENDENCIES>
+      DEPENDS ${RUNNERS_DEPS}
+              $<TARGET_PROPERTY:zephyr_property_target,${TARGET_UPPER}_DEPENDENCIES>
       WORKING_DIRECTORY ${APPLICATION_BINARY_DIR}
       )