message: Add -D<tag> for every tag specified with TAGS=<tag_list>
  This allows for ifdefs in the code based on the tag and is groundwork for kernel refactoring.
  Manually tested that:
  make -f ... TAGS="cmsis-nn abcd-efgh hello_world"
  has these as part of the cflags:
  -DCMSIS_NN -DABCD_EFGH -DHELLO_WORLD
diff: @@ -74,6 +74,20 @@ TEST_SCRIPT := tensorflow/lite/micro/testing/test_linux_binary.sh
  MICROLITE_LIBS := -lm
  +
  +# For each tag specified on the command line we add -D<tag> to the cflags to
  +# allow for #idefs in the code.
  +#
  +# We apply the following transformations (via the tr command):
  +# 1. Convert the tag name to uppercase (TAGS=xtensa_hifimini -> -DXTENSA_HIFIMINI)
  +# 2. (Temporarily) Replace dash with underscore (TAGS=cmsis-nn -> -DCMSIS_NN)
  +#
  +# Transformation 2 is needed because CMSIS-NN is not a valid macro name.
  +#
  +# TODO(b/168824958): remove dash->underscore transformation once the cmsis-nn
  +# and ethos-u directories have been renamed.
  +TAG_DEFINES := $(foreach TAG,$(TAGS),-D$(shell echo $(TAG) | tr [a-z] [A-Z] | tr - _))
  +
  OPTIMIZATION_LEVEL := -O3
  CC_WARNINGS := -Werror -Wsign-compare -Wdouble-promotion \
  @@ -81,8 +95,9 @@ CC_WARNINGS := -Werror -Wsign-compare -Wdouble-promotion \
  -Wunused-function -Wswitch -Wvla
  # TODO(b/150240249): Add in -fno-rtti once that works for the Xtensa toolchain.
  CXXFLAGS := -std=c++11 -Wstrict-aliasing -DTF_LITE_STATIC_MEMORY \
  - $(CC_WARNINGS) $(OPTIMIZATION_LEVEL)
  -CCFLAGS := -DTF_LITE_STATIC_MEMORY $(CC_WARNINGS) $(OPTIMIZATION_LEVEL)
  + $(CC_WARNINGS) $(OPTIMIZATION_LEVEL) $(TAG_DEFINES)
  +CCFLAGS := -DTF_LITE_STATIC_MEMORY $(CC_WARNINGS) $(OPTIMIZATION_LEVEL) \
  + $(TAG_DEFINES)
  ARFLAGS := -r
  # override these in the makefile.inc for specific compiler targets
  