Replace build tools

[pmconrad]

This is an alternative to parts of #1706 - the goal is to facilitate cross-compilation by getting rid of the c++-based build tools cat-parts and embed_genesis.
This PR replaces them with (admittedly somewhat crude) CMake-builtins, instead of the much bigger python scripts in #1706.

Note: the downside is that this PR creates the files during cmake execution, meaning that make won't rebuild if dependencies (i. e. hardfork.d/* or genesis.json) are changed.

[crypto-ape]

Just a little idea to improve developers' experience,

we could warn the developer if he is cross-compiling, that he should consider the GRAPHENE_PREGENERATE_FILES flag.

[pmconrad]

CMake will now detect changes in dependencies of generated files, and re-run itself if required.
Removed the c++-based helpers and the GRAPHENE_PREGENERATE_FILES flag since they are no longer needed.

There is one case that is not handled properly, but that wasn't handled properly before either: adding a new hardfork file in libraries/chain/hardfork.d will not be detected.

[crypto-ape]

I have played a little bit with it.

See here: crypto-ape@6b9a6b1

Using @pmconrad 's CMake scripts I was able to generate the required files, but in a way that is compatible with the old build-flow.

• hardfork.hpp generation is triggered every time the build is run, but the file is rewritten only if there was a change to the hardfork.d directory. This saves compilation time and guarantees that the generated hardfork.hpp is always up to date.

• embed_genesis is triggered only if required and if the source files were changed.

No other dependencies, only CMake.

What do you think, @pmconrad ?

[pmconrad]

Very good. Cherry-picked your changes on top of this branch.

[crypto-ape]

Just tried to compile with MSVC 2015 and it fails.

The line in the generated egenesis_full.cpp is too long.

egenesis_full.cpp(35): error C2026: string too big, trailing characters truncated

According to MSDN "The maximum length of a string literal is 65,535 bytes".

I will try to find a workaround for this.

[pmconrad]

@crypto-ape modified the script to split genesis into chunks of 10k, can you test?

[crypto-ape]

Tested it successfully on Windows with MSVC and MinGW.

Seems good to me.

[pmconrad]

Thanks. @abitmore do you want to test as well?

[abitmore]

I don't want to test, if not necessary :)

[pmconrad]

Can you approve then?