CMake: fix application config

These settings like enable_language should be done in the application and just once.
We hit the issue when you expose sources to an app (interface or public), CMake errors as some of the internal settings have not been configured.

Author: 0xc0170

CMakeLists.txt

@@ -10,17 +10,6 @@ if(POLICY CMP0076)
     cmake_policy(SET CMP0076 NEW)
 endif()
 
-include(${MBED_CONFIG_PATH}/mbed_config.cmake)
-
-# Set default toolchain file
-if(NOT CMAKE_TOOLCHAIN_FILE)
-    set(CMAKE_TOOLCHAIN_FILE "${MBED_ROOT}/tools/cmake/toolchain.cmake" CACHE INTERNAL "")
-endif()
-
-# Toolchain setup
-include(${MBED_ROOT}/tools/cmake/toolchains/${MBED_TOOLCHAIN}.cmake)
-enable_language(C CXX ASM)
-
 include(${MBED_ROOT}/tools/cmake/core.cmake)
 include(${MBED_ROOT}/tools/cmake/profile.cmake)
 

tools/cmake/app.cmake

@@ -0,0 +1,13 @@
+# Copyright (c) 2020 ARM Limited. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+include(${MBED_CONFIG_PATH}/mbed_config.cmake)
+
+# Set default toolchain file
+if(NOT CMAKE_TOOLCHAIN_FILE)
+    set(CMAKE_TOOLCHAIN_FILE "${MBED_ROOT}/tools/cmake/toolchain.cmake" CACHE INTERNAL "")
+endif()
+
+# Toolchain setup
+include(${MBED_ROOT}/tools/cmake/toolchains/${MBED_TOOLCHAIN}.cmake)
+enable_language(C CXX ASM)