message: Update Xtensa build settings to work with the RI2019.2 release.
diff: # Settings for Xtensa XPG toolchain.
  # REQUIRED:
  +# - RI2019.2 Toolkit (for xt-clang/xt-clang++).
  # - XTENSA_CORE: The name of the core to use, will cause a compiler exception
  # without providing a core.
  ifeq ($(TARGET), xtensa-xpg)
  @@ -11,12 +12,11 @@ ifeq ($(TARGET), xtensa-xpg)
  -DTF_LITE_MCU_DEBUG_LOG \
  --xtensa-core=$(XTENSA_CORE) \
  -g -O2 \
  - -fmessage-length=0 \
  - -clang
  + -fmessage-length=0
  TARGET_TOOLCHAIN_PREFIX := xt-
  - CXX_TOOL := xc++
  - CC_TOOL := xcc
  + CXX_TOOL := clang++
  + CC_TOOL := clang
  CXXFLAGS = $(PLATFORM_ARGS) -std=c++11
  CCFLAGS = $(PLATFORM_ARGS) -std=c11
  