Fixed: Non-xcode build workaround for macos with xcode 15 or later in…

…stalled

README.md

@@ -1324,6 +1324,15 @@ cmake -G Xcode ...
 cmake -G Ninja
 ```
 
+>**NOTE**<br/>
+When using MacOS you might run into a few issues caused by the specifics of the platform unrelated to Gaia-ECS. Quick way to fix them is listed bellow.
+>
+> CMake issue:<br/>
+> After you update to a new version of Xcode you might start getting "Ignoring CMAKE_OSX_SYSROOT value: ..." warnings when building the project. Residual cmake cache is to blame here. A solution is to delete files generated by cmake.
+>
+> Linker issue:<br/>
+> When not bulding the project from Xcode and using ***ld*** as your linker, if XCode 15 or later is installed on your system you will most likely run into various issues: https://developer.apple.com/documentation/xcode-release-notes/xcode-15-release-notes#Linking. In the CMake project a workaround is implemented which adds "-Wl,-ld_classic" to linker settings but if you use a different build system or settings you might want to do same.
+
 ### Project settings
 Following is a list of parameters you can use to customize your build
 

src/CMakeLists.txt

@@ -51,6 +51,28 @@ if(MSVC)
 
   enable_cxx_compiler_flag_if_supported("/permissive-")
 else()
+  # MacOS
+  if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Darwin")
+    # Workaround for the new linker starting with XCode 15
+    # https://developer.apple.com/documentation/xcode-release-notes/xcode-15-release-notes#Linking
+    # We need to use -Wl,-ld_classic for the linker for the backwards compatibility when buiding
+    # outside of XCode because they messed things up.
+    if(NOT CMAKE_GENERATOR MATCHES "Xcode")
+      # Make sure xcodebuild is installed. Otherwise we won't be able to tell is the workaround
+      # needs to be applied
+      find_program(XCODEBUILD_EXECUTABLE NAMES xcodebuild)
+
+      if(XCODEBUILD_EXECUTABLE)
+        execute_process(COMMAND xcodebuild -version OUTPUT_VARIABLE XCODE_VERSION_STRING OUTPUT_STRIP_TRAILING_WHITESPACE)
+        string(REGEX MATCH "([0-9]+)\\.[0-9]+" XCODE_MAJOR_VERSION ${XCODE_VERSION_STRING})
+
+        if(XCODE_MAJOR_VERSION GREATER_EQUAL "15")
+          add_link_options("-Wl,-ld_classic")
+        endif()
+      endif()
+    endif()
+  endif()
+
   enable_cxx_compiler_flag_if_supported("-fno-exceptions")
 
   # strictness rules