Revert "nix: adapt cmake options"

This reverts commit c35ed8363f.

nix/cmake-version.patch

@@ -0,0 +1,10 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 6fdf98db..d8424d91 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,4 +1,4 @@
+-cmake_minimum_required(VERSION 3.30)
++cmake_minimum_required(VERSION 3.27)
+ 
+ # Get version
+ file(READ "${CMAKE_SOURCE_DIR}/VERSION" VER_RAW)

nix/default.nix

@@ -53,7 +53,7 @@
   inherit (lib.attrsets) mapAttrsToList;
   inherit (lib.lists) flatten concatLists optional optionals;
   inherit (lib.sources) cleanSourceWith cleanSource;
-  inherit (lib.strings) hasSuffix makeBinPath optionalString mesonBool mesonEnable;
+  inherit (lib.strings) cmakeBool hasSuffix makeBinPath optionalString;
 
   adapters = flatten [
     stdenvAdapters.useMoldLinker
@@ -76,6 +76,14 @@ in
         src = cleanSource ../.;
       };
 
+      patches = [
+        # forces GCC to use -std=c++26
+        ./stdcxx.patch
+
+        # Nix does not have CMake 3.30 yet, so override the minimum version
+        ./cmake-version.patch
+      ];
+
       postPatch = ''
         # Fix hardcoded paths to /usr installation
         sed -i "s#/usr#$out#" src/render/OpenGL.cpp
@@ -144,22 +152,20 @@ in
         (optional withSystemd systemd)
       ];
 
-      mesonBuildType =
+      cmakeBuildType =
         if debug
-        then "debug"
-        else "release";
+        then "Debug"
+        else "RelWithDebInfo";
 
       # we want as much debug info as possible
       dontStrip = debug;
 
-      mesonFlags = flatten [
-        (mapAttrsToList mesonEnable {
-          "xwayland" = enableXWayland;
-          "legacy_renderer" = legacyRenderer;
-          "systemd" = withSystemd;
-        })
-        (mesonBool "b_pch" false)
-      ];
+      cmakeFlags = mapAttrsToList cmakeBool {
+        "NO_XWAYLAND" = !enableXWayland;
+        "LEGACY_RENDERER" = legacyRenderer;
+        "NO_SYSTEMD" = !withSystemd;
+        "CMAKE_DISABLE_PRECOMPILE_HEADERS" = true;
+      };
 
       postInstall = ''
         ${optionalString wrapRuntimeDeps ''

nix/stdcxx.patch

@@ -0,0 +1,12 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index cfbd431f..73e8e0c2 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -64,6 +64,7 @@ endif()
+ include_directories(. "src/" "subprojects/udis86/" "protocols/")
+ set(CMAKE_CXX_STANDARD 26)
+ add_compile_options(
++  -std=c++26
+   -Wall
+   -Wextra
+   -Wno-unused-parameter