Add example with tensor arena in external memory

examples/app_flash_single_model_arena_ext_mem/Makefile

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+TARGET = XCORE-AI-EXPLORER
+APP_NAME =
+
+APP_FLAGS  = -report \
+-O3 -mcmodel=large -fxscope -Wno-xcore-fptrgroup \
+-DSHARED_TENSOR_ARENA \
+-g \
+-lquadflash
+
+# *******************************************************
+# Include AI Tools library and headers
+# *******************************************************
+# The following variables are defined for AI Tools library 
+# and should be included when building the app.
+# XMOS_AITOOLSLIB_DEFINITIONS
+# XMOS_AITOOLSLIB_INCLUDES
+# XMOS_AITOOLSLIB_LIBRARIES
+#
+ifeq ($(XMOS_AITOOLSLIB_PATH),)
+$(error Path to XMOS AI Tools library and headers not set correctly!)
+endif
+include ${XMOS_AITOOLSLIB_PATH}/buildfiles/aitoolslib.make
+
+XCC_FLAGS = $(APP_FLAGS) $(XMOS_AITOOLSLIB_DEFINITIONS) $(XMOS_AITOOLSLIB_INCLUDES)
+XCC_CPP_FLAGS = $(APP_FLAGS) -std=c++14 $(XMOS_AITOOLSLIB_DEFINITIONS) $(XMOS_AITOOLSLIB_INCLUDES)
+XCC_MAP_FLAGS = $(APP_FLAGS) $(XMOS_AITOOLSLIB_LIBRARIES)
+
+#=============================================================================
+# The following part of the Makefile includes the common build infrastructure
+# for compiling XMOS applications. You should not need to edit below here.
+
+XMOS_MAKE_PATH ?= ../..
+include $(XMOS_MAKE_PATH)/xcommon/module_xcommon/build/Makefile.common

examples/app_flash_single_model_arena_ext_mem/README.rst

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+Example with flash and tensor arena on external memory
+==================
+
+Please consult `here <../../docs/rst/flow.rst>`_ on how to install the tools.
+
+This is an example with one network using a tensor arena in external memory.
+This is much slower than having the tensor arena in the 512 kB SRAM, but it allows tensor arenas to have a size larger than 512 kB.
+
+The differences with the ``app_flash_single_model`` example are minimal:
+
+* The shared-arena definition ``-DSHARED_TENSOR_ARENA`` has been added to the
+  Makefile; this allows the application to define the tensor arena buffer.
+
+* In support.cpp a tensor arena is declared in external memory::\
+
+    __attribute__ ((section(".ExtMem.bss")))
+    uint8_t tensor_arena[LARGEST_TENSOR_ARENA_SIZE] __attribute__((aligned(8)));
+
+In order to compile and run this example follow these steps::
+
+  xcore-opt --xcore-weights-file=model.params vww_quant.tflite -o model.tflite
+  mv model.tflite.cpp model.tflite.h src
+  xmake
+  python -c 'from xmos_ai_tools import xformer as xf; xf.generate_flash(
+        output_file="xcore_flash_binary.out",
+        model_files=["model.tflite"],
+        param_files=["model.params"]
+  )'
+  xflash --target XCORE-AI-EXPLORER --data xcore_flash_binary.out
+  xrun --xscope bin/app_flash_single_model.xe
+
+This should print::
+
+  No human (9%)
+  Human (98%)

examples/app_flash_single_model_arena_ext_mem/src/config.xscope

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+<?xml version="1.0" encoding="UTF-8"?>
+
+<xSCOPEconfig ioMode="basic" enabled="true"/>