Merge branch 'bugfix/hide_unsupported_cmake_features_v3.1' into 'release/v3.1'

security: Hide Secure Boot & Flash Encryption config items when using CMake (v3.1)

See merge request espressif/esp-idf!7909

components/bootloader/Kconfig.projbuild

@@ -131,6 +131,7 @@ endmenu  # Bootloader
 
 
 menu "Security features"
+    visible if !IDF_CMAKE
 
 # These three are the actual options to check in code,
 # selected by the displayed options

docs/en/security/flash-encryption.rst

@@ -7,7 +7,11 @@ Flash Encryption is separate from the :doc:`Secure Boot <secure-boot>` feature,
 
 When using any non-default configuration in production, additional steps may also be needed to ensure effectiveness of flash encryption. See :ref:`securing-flash-encryption` for more details.
 
-**IMPORTANT: Enabling flash encryption limits your options for further updates of your ESP32. Make sure to read this document (including :ref:`flash-encryption-limitations`) and understand the implications of enabling flash encryption.**
+.. important::
+    Enabling flash encryption limits your options for further updates of your ESP32. Make sure to read this document (including :ref:`flash-encryption-limitations`) and understand the implications of enabling flash encryption.
+
+.. note::
+    Flash encryption is only supported when using the default GNU Make build system. The CMake build system preview in ESP-IDF v3.x does not support flash encryption.
 
 Background
 ----------

docs/en/security/secure-boot.rst

@@ -9,6 +9,10 @@ Secure Boot is separate from the :doc:`Flash Encryption <flash-encryption>` feat
 
     Enabling secure boot limits your options for further updates of your ESP32. Make sure to read this document throughly and understand the implications of enabling secure boot.
 
+.. note::
+
+    Secure boot is only supported when using the default GNU Make build system. The CMake build system preview in ESP-IDF v3.x does not support secure boot.
+
 Background
 ----------