fix cmake warning

CMake/toolchain.cmake

@@ -74,16 +74,8 @@ if((NOT DEFINED YOTTA_CFG_GCC_PRINTF_FLOAT) OR (YOTTA_CFG_GCC_PRINTF_FLOAT))
 endif()
 
 # Set the compiler to ARM-GCC
-if(CMAKE_VERSION VERSION_LESS "3.6.0")
-    include(CMakeForceCompiler)
-    cmake_force_c_compiler("${ARM_NONE_EABI_GCC}" GNU)
-    cmake_force_cxx_compiler("${ARM_NONE_EABI_GPP}" GNU)
-else()
-    # from 3.5 the force_compiler macro is deprecated: CMake can detect
-    # arm-none-eabi-gcc as being a GNU compiler automatically
-    set(CMAKE_C_COMPILER "${ARM_NONE_EABI_GCC}")
-    set(CMAKE_CXX_COMPILER "${ARM_NONE_EABI_GPP}")
-endif()
+set(CMAKE_C_COMPILER "${ARM_NONE_EABI_GCC}")
+set(CMAKE_CXX_COMPILER "${ARM_NONE_EABI_GPP}")
 
 # post-process elf files into .bin files:
 function(yotta_apply_target_rules target_type target_name)