Add support for building via CMake

[Hagb]

The way to load embedded files is also changed, to avoid potential confusion.

[Hagb]

(It still has some problems, so I make it a draft until I fix it.)

[Hagb]

(Change Debug to Release if you expect a release build)
Build on *nix (and Windows?):

mkdir build-tmp; cd build-tmp
# --install-prefix=/path/to/th155/ is optional.
# On Debian based distro you might need to add also -DCLANG_SUFFIX=-18 argument.
cmake --install-prefix="/path/to/th155/" -DCMAKE_BUILD_TYPE=Debug ..
cmake --build . --parallel
# (optional) copy files to th155 directory. (`--prefix=/path/to/th155/` is optional if it has been correctly set.)
cmake --install . --prefix="/path/to/th155/"

Build on with multi-config generators such as Visual Studio Generator:

mkdir build-tmp; cd build-tmp
cmake --install-prefix="/path/to/th155/" ..
cmake --build . --config Debug --parallel
cmake --install . --config Debug --prefix="/path/to/th155/"

(Change Debugs to Release to get release builds.)
edited: add --parallel for cmake --build
edited: --toolchain= and -T ClangCL -A Win32 are no longer needed.