Add root Makefile to keep all compiler/linker options about mipt-mips

[gkorepanov]

Well, I have studied the question a bit. I'm wondering what exactly we are going to achieve. The variants are:

• The recursive build system which allows to build any module (like func_instr) independently or to build a whole project.
  This is mainly considered not to be the best way to go: Recursive Make Considered Harmful

• The non-recursive build system allowing for different targets and wise multi-level include system, which would allow to build the whole project in a moment as well (I do consider this way to be best, as the project grows and we are already having cross-dependencies (just look at the perf_sim Makefile with a number of vpath statements, or probably consider the gtest lib necessary for almost any module))

• Just few independent Makefiles sharing the common code in the top-level one (it's the closest to what we have now but don't seem to be brilliant in my view)

• Whatever else...?

[pavelkryukov]

@igorsmir-ilab Igor, what do you think?

[igorsmir-ilab]

I would say let's stick to the easiest option for now - few independent Makefiles with shared root. This will allow us to solve current task - central CXXFLAGS definition, as well as enable faster forward progress with very strict C++ warnings issue #44.

The non-recursive build system could be set as the next milestone, IMO.

[gkorepanov]

I'm now adding the header dependencies to all Makefiles and it looks that all of them (Makefiles) are becoming quite similar. Probably I should make a root Makefile with common rules as well?

[pavelkryukov]

It is not critical now but can create some problems to current users as they won't expect significant build changes. Let's postpone that for now.

[gkorepanov]

Ok, thanks.

[pavelkryukov]

WIP on testing changes