CMake: Set compile defintions for supported toolchain at top level input source file

The compile defintions should always be added depending on the
selected toolchain.
mbed_set_toolchain_options() should only be called if a third-party
toolchain file has not been used as it has compile options that can
cause conflicts.

CMakeLists.txt

@@ -10,6 +10,7 @@ if(POLICY CMP0076)
     cmake_policy(SET CMP0076 NEW)
 endif()
 
+include(${MBED_CONFIG_PATH}/mbed_config.cmake)
 include(${MBED_PATH}/tools/cmake/core.cmake)
 include(${MBED_PATH}/tools/cmake/profile.cmake)
 
@@ -74,6 +75,22 @@ target_compile_definitions(mbed-core
         ${MBED_CONFIG_DEFINITIONS}
 )
 
+# Add compile definitions for backward compatibility with the toolchain
+# supported. New source files should instead check for __GNUC__ and __clang__
+# for the GCC_ARM and ARM toolchains respectively. 
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    target_compile_definitions(mbed-core
+        INTERFACE
+            TOOLCHAIN_GCC_ARM
+            TOOLCHAIN_GCC
+    )
+elseif(${MBED_TOOLCHAIN} STREQUAL "ARM")
+    target_compile_definitions(mbed-core
+        INTERFACE
+            TOOLCHAIN_ARM
+    )
+endif()
+
 # Include mbed.h and config from generate folder
 target_include_directories(mbed-core
     INTERFACE

tools/cmake/toolchains/ARM.cmake

@@ -13,7 +13,6 @@ if(MBEDIDE)
     set_property(GLOBAL PROPERTY MBED_STUDIO_ARM_COMPILER "--ide=mbed")
 endif()
 
-
 # Sets toolchain options
 function(mbed_set_toolchain_options target)
     get_property(mbed_studio_arm_compiler GLOBAL PROPERTY MBED_STUDIO_ARM_COMPILER)
@@ -48,11 +47,6 @@ function(mbed_set_toolchain_options target)
             $<$<COMPILE_LANGUAGE:ASM>:${MBED_STUDIO_ARM_COMPILER}>
     )
 
-    target_compile_definitions(${target}
-        INTERFACE
-            TOOLCHAIN_ARM
-    )
-
     list(APPEND link_options
         "${MBED_STUDIO_ARM_COMPILER}"
         "--map"

tools/cmake/toolchains/GCC_ARM.cmake

@@ -7,7 +7,6 @@ set(CMAKE_CXX_COMPILER "arm-none-eabi-g++")
 set(GCC_ELF2BIN "arm-none-eabi-objcopy")
 set_property(GLOBAL PROPERTY ELF2BIN ${GCC_ELF2BIN})
 
-
 # Sets toolchain options
 function(mbed_set_toolchain_options target)
     list(APPEND link_options
@@ -52,13 +51,6 @@ function(mbed_set_toolchain_options target)
             ${common_options}
     )
 
-    target_compile_definitions(${target}
-        INTERFACE
-            TOOLCHAIN_GCC_ARM
-            TOOLCHAIN_GCC
-    )
-
-
     target_link_options(${target}
         INTERFACE
             ${common_options}