add HACK file
diff --git a/HACK b/HACK
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+Capstone source is organized as followings.
+
+. <- core engine + README + COMPILE etc
+├── arch <- code handling disasm for each arch
+│ ├── AArch64 <- ARM64 (aka ARMv8)
+│ ├── ARM <- ARM
+│ ├── Mips <- Mips
+│ └── X86 <- X86
+├── bindings <- all bindings
+│ ├── csharp <- C# bindings + test code
+│ ├── java <- Java bindings + test code
+│ ├── ocaml <- Ocaml bindings + test code
+│ ├── python <- Python bindings + test code
+│ └── ruby <- Ruby bindings + test code
+├── include <- API headers in C (*.h)
+├── release <- Precompiled binaries
+│ ├── linux
+│ ├── mac
+│ └── windows
+├── tests <- Test code (in C)
+
+
+Follow COMPILE to see how to compile and run code.
+Note: if you find some bugs during compilation, it is recommended to clean
+the code and try again, for example with:
+
+ $ make clean
+ $ make
+
+