CMake: Explicitly set CMAKE_OSX_SYSROOT to macosx for macOS host builds

The implicit default CMAKE_OSX_SYSROOT was a workaround in CMake for
macOS ~10.8. As of CMake 4.x, CMake expects macOS host compilers to have
their own default sysroot detection logic. However, upstream llvm does
not actually do this, only Apple Clang does. To keep supporting homebrew
clang and manually compiled clang from llvm/llvm-project, we need to
set the sysroot explicitly.

The behavior difference and lack of default detection logic in the clang
driver is tracked at https://gitlab.kitware.com/cmake/cmake/-/issues/26863

CMakeLists.txt

@@ -15,6 +15,10 @@ if (CMAKE_TOOLCHAIN_FILE MATCHES "vcpkg.cmake$")
     set(CMAKE_PROJECT_ladybird_INCLUDE_BEFORE "Meta/CMake/vcpkg/generate_vcpkg_toolchain_variables.cmake")
 endif()
 
+if (APPLE AND NOT CMAKE_OSX_SYSROOT)
+    set(CMAKE_OSX_SYSROOT macosx)
+endif()
+
 project(ladybird
         VERSION 0.1.0
         LANGUAGES C CXX

Meta/CMake/vcpkg/base-triplets/arm64-osx.cmake

@@ -2,5 +2,6 @@ set(VCPKG_CMAKE_SYSTEM_NAME Darwin)
 set(VCPKG_TARGET_ARCHITECTURE arm64)
 set(VCPKG_OSX_ARCHITECTURES arm64)
 set(VCPKG_CRT_LINKAGE dynamic)
+set(VCPKG_OSX_SYSROOT macosx)
 
 include(${CMAKE_CURRENT_LIST_DIR}/base.cmake)

Meta/CMake/vcpkg/base-triplets/x64-osx.cmake

@@ -2,5 +2,6 @@ set(VCPKG_CMAKE_SYSTEM_NAME Darwin)
 set(VCPKG_TARGET_ARCHITECTURE x64)
 set(VCPKG_OSX_ARCHITECTURES x86_64)
 set(VCPKG_CRT_LINKAGE dynamic)
+set(VCPKG_OSX_SYSROOT macosx)
 
 include(${CMAKE_CURRENT_LIST_DIR}/base.cmake)

Meta/Lagom/BuildFuzzers.sh

@@ -60,7 +60,6 @@ cmake -GNinja --preset=Distribution -B Build/tools \
     -DCMAKE_INSTALL_PREFIX=Build/tool-install \
     -DCMAKE_C_COMPILER=$BEST_CLANG_CANDIDATE \
     -DCMAKE_CXX_COMPILER="${BEST_CLANG_CANDIDATE/clang/clang++}" \
-    -DCMAKE_OSX_SYSROOT=macosx \
     -Dpackage=LagomTools
 ninja -C Build/tools install
 

Meta/Lagom/CMakeLists.txt

@@ -1,5 +1,9 @@
 cmake_minimum_required (VERSION 3.21)
 
+if (APPLE AND NOT CMAKE_OSX_SYSROOT)
+    set(CMAKE_OSX_SYSROOT macosx)
+endif()
+
 project(
     Lagom
     VERSION 0.0.0