Stop using git for the version tag.
The new process is as follows:
1. The `VERSION` file contains the version.
For release, it should contain "1.5.0".
Immediately after the release, it should be changed to "1.6.0-dev".
2. The build type is included in the version string unless it is
"Release". The commit hash is now included into the version string
whenever the `VERSION` file has a suffix (i.e. 1.5.0-dev rather than
just 1.5.0). The full version string for development builds now
looks like this: `1.5.0-dev-Debug-b102dccf8`.
This means we longer need git or `-DVERSION_NUM` to get a sensible version number.
The in-development versions are now always clearly indicated with the
`-dev` suffix no matter how DevilutionX was built.
1. Platform and toolchain files are now all under `platforms/`, with a
single `CMake/platforms/${platform}.cmake` per platform.
2. Custom functions/macros are under `functions/`.
3. Finder modules are in `/finders`.
Generator expressions are the only way to distinguish between build
types in multi-configuration builds (Visual Studio).
This adds generator expressions for some of build type dependent
values as a starting point.
See a more detailed explanation at:
https://cmake.org/cmake/help/latest/manual/cmake-buildsystem.7.html#build-specification-with-generator-expressions
Notably:
> Some buildsystems generated by cmake(1) have a predetermined build-configuration set in the CMAKE_BUILD_TYPE variable. The buildsystem for the IDEs such as Visual Studio and Xcode are generated independent of the build-configuration, and the actual build configuration is not known until build-time. Therefore, code such as
>
> string(TOLOWER ${CMAKE_BUILD_TYPE} _type)
> if (_type STREQUAL debug)
> target_compile_definitions(exe1 PRIVATE DEBUG_BUILD)
> endif()
>
> may appear to work for Makefile Generators and Ninja generators, but is not portable to IDE generators.
1. Move `project` before `check_ipo_supported`, so that the check knows
the languages to check.
2. Better error message if LTO is not supported.
3. Use a separate flag for LTO
4. Enable LTO for the nightly build.
5. Move git commands to a separate file.
Gleb Mazovetskiy