Fix: update the README stating what changed with CMake

README.md

@@ -513,46 +513,40 @@ create one after closing.
 
 ## 7.0) Compiling
 
-### Windows:
+### Windows
 
-You need Microsoft Visual Studio 2015 Update 3 or more recent. Open the project file
-and it should build automatically. In case you want to build with SDL support
-you need to add WITH_SDL to the project settings.
+You need Microsoft Visual Studio 2017 or more recent. You can open the folder
+(as a CMake project). CMake will be detected, and you can compile from there.
 
 PNG (WITH_PNG), ZLIB (WITH_ZLIB), LZO (WITH_LZO), Freetype (WITH_FREETYPE) and
-libLZMA (WITH_LIBLZMA) support is enabled by default. For these to work you need their
-development files. To get them just use vcpkg from https://github.com/Microsoft/vcpkg
-using x86-windows-static and x64-windows-static triplets.
-For more help with VS see docs/Readme_Windows_MSVC.md.
-
-You can also build it using the Makefile with MSYS/MinGW or Cygwin/MinGW.
-Please read the Makefile for more information.
-
-### Solaris, FreeBSD, OpenBSD:
-
-Use '`gmake`', but do a '`./configure`' before the first build.
-
-### Linux/Unix:
-
-OpenTTD can be built with GNU '`make`'. On non-GNU systems it is called '`gmake`'.
-However, for the first build one has to do a '`./configure`' first.
-
-### macOS:
-
-Use '`make`' or Xcode (which will then call make for you)
-This will give you a binary for your CPU type (PPC/Intel)
-However, for the first build one has to do a '`./configure`' first.
-To make a universal binary type '`./configure --enabled-universal`'
-instead of '`./configure`'.
-
-### Haiku:
-
-Use '`make`', but do a '`./configure`' before the first build.
-
-### OS/2:
-
-A comprehensive GNU build environment is required to build the OS/2 version.
-See the docs/Readme_OS2.txt file for more information.
+libLZMA (WITH_LIBLZMA) support is enabled by default. For these to work you
+need their development files. To get them just use vcpkg from
+https://github.com/Microsoft/vcpkg using x86-windows-static and
+x64-windows-static triplets. For more help with VS see
+docs/Readme_Windows_MSVC.md.
+
+Alternatively, you can create a MSVC project file via CMake. For this
+either download CMake from https://cmake.org/download/ or use the version
+that comes with vcpkg. After that, you can run something similar to this:
+
+```powershell
+mkdir build
+cd build
+cmake.exe .. -G'Visual Studio 16 2019' -DCMAKE_TOOLCHAIN_FILE="<location of vcpkg>\vcpkg\scripts\buildsystems\vcpkg.cmake" -DVCPKG_TARGET_TRIPLET="x64-windows-static"
+```
+
+Change `<location of vcpkg>` to where you have installed vcpkg. After this
+in the build folder are MSVC project files. MSVC can rebuild the project
+files himself via the `ZERO_CHECK` project.
+
+### All other platforms
+
+```bash
+mkdir build
+cd build
+cmake ..
+make
+```
 
 ### 7.1) Required/optional libraries
 
@@ -577,50 +571,42 @@ no graphical user interface; you would be building a dedicated server.
 
 ### 7.2) Supported compilers
 
-The following compilers are known to compile OpenTTD:
-
-- Microsoft Visual C++ (MSVC) 2015, 2017 and 2019.
-- GNU Compiler Collection (GCC) 3.3 - 4.4, 4.6 - 4.8.
-    - Versions 4.1 and earlier give bogus warnings about uninitialised variables.
-    - Versions 4.4, 4.6 give bogus warnings about freeing non-heap objects.
-    - Versions 4.6 and later give invalid warnings when lto is enabled.
-- Intel C++ Compiler (ICC) 12.0.
-- Clang/LLVM 2.9 - 3.0
-   Version 2.9 gives bogus warnings about code nonconformity.
-
-The following compilers are known not to compile OpenTTD:
-
-- Microsoft Visual C++ (MSVC) 2013 and earlier.
-   These old versions do not support modern C++ language features.
-- GNU Compiler Collection (GCC) 3.2 and earlier.
-   These old versions fail due to OpenTTD's template usage.
-- GNU Compiler Collection (GCC) 4.5. It optimizes enums too aggressively.
-   See https://github.com/OpenTTD/OpenTTD/issues/5513 and references therein.
-- Intel C++ Compiler (ICC) 11.1 and earlier.
-    - Version 10.0 and earlier fail a configure check and fail with recent
-       system headers.
-    - Version 10.1 fails to compile station_gui.cpp.
-    - Version 11.1 fails with an internal error when compiling network.cpp.
-- Clang/LLVM 2.8 and earlier.
-- (Open) Watcom.
-
-If any of these compilers can compile OpenTTD again, please let us know.
-Patches to support more compilers are welcome.
+Every compiler that is supported by CMake and supports C++11, should be
+able to compile OpenTTD. As the exact list of compilers changes constantly,
+we refer to the compiler manual to see if it supports C++11, and to CMake
+to see if it supports your compiler.
 
 ### 7.3) Compilation of base sets
 
 To recompile the extra graphics needed to play with the original Transport
 Tycoon Deluxe graphics you need GRFCodec (which includes NFORenum) as well.
-GRFCodec can be found at https://www.openttd.org/download-grfcodec.
-The compilation of these extra graphics does generally not happen, unless
-you remove the graphics file using '`make maintainer-clean`'.
-
-Re-compilation of the base sets, thus also use of '`--maintainer-clean`' can
-leave the repository in a modified state as different grfcodec versions can
-cause binary differences in the resulting grf. Also translations might have
-been added for the base sets which are not yet included in the base set
-information files. Use the configure option '`--without-grfcodec`' to avoid
-modification of the base set files by the build process.
+GRFCodec can be found at
+https://www.openttd.org/downloads/grfcodec-releases/latest.html.
+
+Having GRFCodec installed can cause regeneration of the `.grf` files, which
+are written in the source directory. This can leave your repository in a
+modified state, as different GRFCodec versions can cause binary differences
+in the resulting `.grf` files. Also translations might have been added for
+the base sets which are not yet included in the base set information files.
+To avoid this behaviour, disable GRFCodec (and NFORenum) in CMake cache
+(`GRFCODEC_EXECUTABLE` and `NFORENUM_EXECUTABLE`).
+
+### 7.4) Developers settings
+
+You can control some flags directly via `CXXFLAGS` (any combination
+of these flags will work fine too):
+
+- `-DRANDOM_DEBUG`: this helps with debugging desyncs.
+- `-fno-inline`: this avoids creating inline functions; this can make
+  debugging a lot easier.
+- `-O0`: this disables all optimizations; this can make debugging a
+  lot easier.
+- `-p`: this enables profiling.
+
+Always use a clean buildfolder if you changing `CXXFLAGS`, as this
+value is otherwise cached. Example use:
+
+`CXXFLAGS="-fno-inline" cmake ..`
 
 ## 8.0) Translating