add IAR support for G0 with cmake

tools/cmake/toolchain/arm_gcc.cmake

@@ -1,8 +1,8 @@
 set(CMAKE_SYSTEM_NAME Generic)
 
-set(CMAKE_ASM_COMPILER "arm-none-eabi-gcc")
 set(CMAKE_C_COMPILER "arm-none-eabi-gcc")
 set(CMAKE_CXX_COMPILER "arm-none-eabi-g++")
+set(CMAKE_ASM_COMPILER "arm-none-eabi-gcc")
 
 set(CMAKE_SIZE "arm-none-eabi-size" CACHE FILEPATH "")
 set(CMAKE_OBJCOPY "arm-none-eabi-objcopy" CACHE FILEPATH "")
@@ -29,13 +29,13 @@ list(APPEND TOOLCHAIN_COMMON_FLAGS
   -fno-strict-aliasing
   )
 
-list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
+set(TOOLCHAIN_EXE_LINKER_FLAGS
   -Wl,--print-memory-usage
   -Wl,--gc-sections
   -Wl,--cref
   )
 
-list(APPEND TOOLCHAIN_WARNING_FLAGS
+set(TOOLCHAIN_WARNING_FLAGS
   -Wall
   -Wextra
   -Werror
@@ -62,3 +62,11 @@ list(APPEND TOOLCHAIN_WARNING_FLAGS
   )
 
 include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)
+
+# try_compile is cmake test compiling its own example,
+# pass -nostdlib to skip stdlib linking
+get_property(IS_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE)
+if (IS_IN_TRY_COMPILE)
+  set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -nostdlib")
+  set(CMAKE_CXX_LINK_FLAGS "${CMAKE_CXX_LINK_FLAGS} -nostdlib")
+endif ()