fix cmake build

examples/cmake/toolchain/arm_gcc.cmake

@@ -0,0 +1,54 @@
+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(GCC_ELF2BIN "arm-none-eabi-objcopy")
+set_property(GLOBAL PROPERTY ELF2BIN ${GCC_ELF2BIN})
+
+# Look for includes and libraries only in the target system prefix.
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+
+# pass TOOLCHAIN_CPU to
+set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES CMAKE_SYSTEM_PROCESSOR)
+
+include(${CMAKE_CURRENT_LIST_DIR}/../cpu/${CMAKE_SYSTEM_PROCESSOR}.cmake)
+
+# enable all possible warnings for building examples
+list(APPEND TOOLCHAIN_COMMON_FLAGS
+  -fdata-sections
+  -ffunction-sections
+  -fsingle-precision-constant
+  -fno-strict-aliasing
+  )
+
+set(TOOLCHAIN_WARNING_FLAGS
+  -Wall
+  -Wextra
+  -Werror
+  -Wfatal-errors
+  -Wdouble-promotion
+  -Wstrict-prototypes
+  -Wstrict-overflow
+  -Werror-implicit-function-declaration
+  -Wfloat-equal
+  -Wundef
+  -Wshadow
+  -Wwrite-strings
+  -Wsign-compare
+  -Wmissing-format-attribute
+  -Wunreachable-code
+  -Wcast-align
+  -Wcast-function-type
+  -Wcast-qual
+  -Wnull-dereference
+  -Wuninitialized
+  -Wunused
+  -Wreturn-type
+  -Wredundant-decls
+  )
+
+include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)