message: Fix zephyr_riscv build process
  This adds additional compiler flags for Zephyr applications
  in order to eliminate compilation warnings that are treated as errors.
  Additionally, the `-fno-threadsafe-statics` switch can be applied to C++ files only.
diff: @@ -2,13 +2,11 @@ cmake_minimum_required(VERSION 3.13.1)
  include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
  project(tf_lite_magic_wand)
  -set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} %{CXX_FLAGS}%")
  +# -fno-threadsafe-statics -- disables the mutex around initialization of local static variables
  +set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} %{CXX_FLAGS}% -fno-threadsafe-statics -Wno-sign-compare -Wno-narrowing")
  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} %{CC_FLAGS}%")
  set(CMAKE_EXE_LINKER_FLAGS "%{LINKER_FLAGS}%")
  -# -fno-threadsafe-statics -- disables the mutex around initialization of local static variables
  -target_compile_options(app PRIVATE "-fno-threadsafe-statics")
  -
  target_sources(app PRIVATE
  %{SRCS}%
  )
  