[SH] Fix build warnings

[Rot127]

These commits add several build warning options to CMakeList.txt and fixes build warnings for the SH arch.
Two unused functions are removed and a parantheses/int-in-bool-contexxt warning is fixed.

@ysat0 Could you please take a look at it as well?

[Rot127]

Anyone has an idea why MSVC != true for the failing test? Unfortunately, I currently don't have a Windows machine for debugging.

[ysat0]

I also don't have an environment where I can use MSVC right now.
I will prepare and check it in the next week.

[ysat0]

Fixed.
ysat0@0eebf32
It looks like cmake can't detect MSVC.
I've verified that this change builds on Windows/MSVC and Linux/gcc.

[Rot127]

The build seems to fail with this as well. Or am I missing something?
We could also just remove the build options and open an issue about it. If everyone is fine with it.

[kabeor]

Hi, you need to define what MSVC is here

[Rot127]

It should be predefined by cmake. See: https://cmake.org/cmake/help/latest/variable/MSVC.html
But it isn't in our case.

[Rot127]

Wait. I haven't tried this last time. Doesn't work

[XVilka]

@Rot127 I think I might know the reason - this variable probably doesn't work before the project() clause.

See also https://stackoverflow.com/questions/41692725/cmake-doesnt-recognize-msvc-compiler#41693234

[Rot127]

This was it. Thanks!

[XVilka]

LGTM

[kabeor]

Great, Thank you!