Replace Schema.s with generated .cpp file

This removes the dependency on an assembler (which must support .incbin).
Instead we use xxd as a custom build command to generate a .cpp file
which is included in the build.

This makes it possible to build on Windows, for which you need 
cp.exe (from GNU Core Utils) and xxd.exe (from Vim).

Change-Id: I3a929640b1fdbfc27e2c38abd05bf3a298245ba5
Signed-off-by: Robert Hughes <robert.hughes@arm.com>
diff --git a/src/armnnTfLiteParser/test/Schema.hpp b/src/armnnTfLiteParser/test/Schema.hpp
index 49ecc0e..2438115 100644
--- a/src/armnnTfLiteParser/test/Schema.hpp
+++ b/src/armnnTfLiteParser/test/Schema.hpp
@@ -3,7 +3,5 @@
 // SPDX-License-Identifier: MIT
 //
 
-extern "C" {
-extern const char tflite_schema_start;
-extern const char tflite_schema_end;
-}
+extern unsigned char g_TfLiteSchemaText[];
+extern unsigned int g_TfLiteSchemaText_len;