CMake: use CMAKE_TOOLCHAIN_FILE

We should define CMAKE_TOOLCHAIN_FILE (as we are providing Mbed OS toolchain file). This fixes
also the issue we had with Unix makefiles where application would be without response files.

For more details, see https://gitlab.kitware.com/cmake/cmake/-/issues/21104

As the Mbed OS toolchain file is included by CMake, we need to have enabling language in the main CMake (can be executed
only once).

Author: 0xc0170

CMakeLists.txt

@@ -10,23 +10,29 @@ if(POLICY CMP0076)
     cmake_policy(SET CMP0076 NEW)
 endif()
 
-# Create Mbed OS library
-add_library(mbed-os OBJECT)
-
 include(${MBED_CONFIG_PATH}/mbed_config.cmake)
 
+# Set default toolchain file
+if(NOT CMAKE_TOOLCHAIN_FILE)
+    set(CMAKE_TOOLCHAIN_FILE "${MBED_ROOT}/cmake/toolchain.cmake" CACHE INTERNAL "")
+endif()
+
+# Toolchain setup
+include(${MBED_ROOT}/cmake/toolchains/${MBED_TOOLCHAIN}.cmake)
+enable_language(C CXX ASM)
+
 include(${MBED_ROOT}/cmake/core.cmake)
-mbed_set_cpu_core_options(mbed-os ${MBED_TOOLCHAIN})
+include(${MBED_ROOT}/cmake/util.cmake)
+include(${MBED_ROOT}/cmake/profile.cmake)
 
-include(${MBED_ROOT}/cmake/toolchain.cmake)
+# Create Mbed OS library
+add_library(mbed-os OBJECT)
+
+mbed_set_cpu_core_options(mbed-os ${MBED_TOOLCHAIN})
 mbed_set_toolchain_options(mbed-os)
 mbed_set_language_standard(mbed-os)
-
-include(${MBED_ROOT}/cmake/profile.cmake)
 mbed_set_profile_options(mbed-os ${MBED_TOOLCHAIN})
 
-include(${MBED_ROOT}/cmake/util.cmake)
-
 set_target_properties(mbed-os
     PROPERTIES
         MBED_TARGET_LABELS "${MBED_TARGET_LABELS}"

cmake/toolchain.cmake

@@ -40,19 +40,12 @@ elseif (MBED_CPU_CORE STREQUAL Cortex-M7FD)
     set(CMAKE_SYSTEM_PROCESSOR cortex-m7)
 endif()
 
-
-
-include(${MBED_ROOT}/cmake/toolchains/${MBED_TOOLCHAIN}.cmake)
-
 # Compiler setup
 set(CMAKE_SYSTEM_NAME Generic)
 set(CMAKE_CROSSCOMPILING TRUE)
 set(CMAKE_C_COMPILER_WORKS TRUE)
 set(CMAKE_CXX_COMPILER_WORKS TRUE)
 
-# Project setup
-enable_language(C CXX ASM)
-
 # Set the language standard to use per target
 function(mbed_set_language_standard target)
     set_target_properties(${target}