cmake: segger: linker_script: handle section rtt_buff_data

The segger cmake linker script is out of date compared to
segger_rtt.ld. This is causing linker failures with IAR
when segger is enabled (on nrf hardware for example).

Signed-off-by: Carl Eriksson Skogh <carl.erikssonskogh@gmail.com>

modules/segger/CMakeLists.txt

@@ -13,6 +13,8 @@ if(CONFIG_USE_SEGGER_RTT)
   zephyr_library_sources_ifdef(CONFIG_SEGGER_SYSTEMVIEW ${SEGGER_DIR}/SEGGER/SEGGER_SYSVIEW.c)
   # Using sort key AAA to ensure that we are placed at start of RAM
   zephyr_linker_sources_ifdef(CONFIG_SEGGER_RTT_SECTION_CUSTOM RAM_SECTIONS SORT_KEY aaa segger_rtt.ld)
+  zephyr_linker_section_ifdef(CONFIG_SEGGER_RTT_SECTION_CUSTOM NAME "rtt_buff_data" GROUP RAM_REGION ALIGN 4 NOINPUT)
+  zephyr_linker_section_configure(SECTION "rtt_buff_data" INPUT "${CONFIG_SEGGER_RTT_SECTION_CUSTOM_NAME}" SYMBOLS )
 endif()
 
 if(CONFIG_SEGGER_DEBUGMON)