message: Add the ability to specify the version of a Hexagon CPU
diff: # - Hexagon SDK 3.5 Toolkit (for hexagon-clang++, hexagon-sim).
  # - HEXAGON_SDK_PREFIX environment variable must be set to location of
  # Hexagon_SDK/<version>/ on your machine.
  +# - HEXAGON_CPU_VER: The CPU version to use, will cause a compiler exception
  +# without providing a version. Acceptable values: v55-v67
  #
  # Unlike other targets, there is not currently a way to automatically download
  # the Hexagon SDK. For this reason, users are required to manually download
  @@ -42,8 +44,8 @@ ifeq ($(TARGET), hexagon)
  -fomit-frame-pointer \
  -fpermissive \
  -funsigned-char \
  - -mcpu=v66 \
  - -mv66
  + -mcpu=$(HEXAGON_CPU_VER) \
  + -m$(HEXAGON_CPU_VER)
  TARGET_TOOLCHAIN_PREFIX := hexagon-
  CXX_TOOL := clang++
  