cmake: Adjust macOS SDK detection

Change in-line with OBS's Master branch : https://github.com/obsproject/obs-studio/blob/master/cmake/macos/compilerconfig.cmake

Fix errors when macOS SDK is not detected when using cmake 4.0.0+

cmake/macos/compilerconfig.cmake

@@ -15,22 +15,48 @@ include(compiler_common)
 add_compile_options("$<$<NOT:$<COMPILE_LANGUAGE:Swift>>:-fopenmp-simd>")
 
 # Ensure recent enough Xcode and platform SDK
-set(_obs_macos_minimum_sdk 15.0) # Keep in sync with Xcode
-set(_obs_macos_minimum_xcode 16.0) # Keep in sync with SDK
-message(DEBUG "macOS SDK Path: ${CMAKE_OSX_SYSROOT}")
-string(REGEX MATCH ".+/MacOSX.platform/Developer/SDKs/MacOSX([0-9]+\\.[0-9])+\\.sdk$" _ ${CMAKE_OSX_SYSROOT})
-set(_obs_macos_current_sdk ${CMAKE_MATCH_1})
-message(DEBUG "macOS SDK version: ${_obs_macos_current_sdk}")
-if(_obs_macos_current_sdk VERSION_LESS _obs_macos_minimum_sdk)
-  message(
-    FATAL_ERROR
-    "Your macOS SDK version (${_obs_macos_current_sdk}) is too low. "
-    "The macOS ${_obs_macos_minimum_sdk} SDK (Xcode ${_obs_macos_minimum_xcode}) is required to build OBS."
+function(check_sdk_requirements)
+  set(obs_macos_minimum_sdk 15.0) # Keep in sync with Xcode
+  set(obs_macos_minimum_xcode 16.0) # Keep in sync with SDK
+  execute_process(
+    COMMAND xcrun --sdk macosx --show-sdk-platform-version
+    OUTPUT_VARIABLE obs_macos_current_sdk
+    RESULT_VARIABLE result
+    OUTPUT_STRIP_TRAILING_WHITESPACE
   )
-endif()
-unset(_obs_macos_current_sdk)
-unset(_obs_macos_minimum_sdk)
-unset(_obs_macos_minimum_xcode)
+  if(NOT result EQUAL 0)
+    message(
+      FATAL_ERROR
+      "Failed to fetch macOS SDK version. "
+      "Ensure that the macOS SDK is installed and that xcode-select points at the Xcode developer directory."
+    )
+  endif()
+  message(DEBUG "macOS SDK version: ${obs_macos_current_sdk}")
+  if(obs_macos_current_sdk VERSION_LESS obs_macos_minimum_sdk)
+    message(
+      FATAL_ERROR
+      "Your macOS SDK version (${obs_macos_current_sdk}) is too low. "
+      "The macOS ${obs_macos_minimum_sdk} SDK (Xcode ${obs_macos_minimum_xcode}) is required to build OBS."
+    )
+  endif()
+  execute_process(COMMAND xcrun --find xcodebuild OUTPUT_VARIABLE obs_macos_xcodebuild RESULT_VARIABLE result)
+  if(NOT result EQUAL 0)
+    message(
+      FATAL_ERROR
+      "Xcode was not found. "
+      "Ensure you have installed Xcode and that xcode-select points at the Xcode developer directory."
+    )
+  endif()
+  message(DEBUG "Path to xcodebuild binary: ${obs_macos_xcodebuild}")
+  if(XCODE_VERSION VERSION_LESS obs_macos_minimum_xcode)
+    message(
+      FATAL_ERROR
+      "Your Xcode version (${XCODE_VERSION}) is too low. Xcode ${obs_macos_minimum_xcode} is required to build OBS."
+    )
+  endif()
+endfunction()
+
+check_sdk_requirements()
 
 # Enable dSYM generator for release builds
 string(APPEND CMAKE_C_FLAGS_RELEASE " -g")