Fix Xcode 15 linker warning

XCode 15 includes a completely new linker implementation.
Hence some flags are deprecated.

The default is now error so we can simply remove the linker option.

CMakeLists.txt

@@ -142,10 +142,12 @@ if(${CMAKE_CXX_COMPILER_ID} MATCHES "GNU")
         add_compile_options(-Werror=deprecated-copy)
     endif()
 
-    if(NOT CMAKE_SYSTEM_NAME STREQUAL "OpenBSD" AND NOT CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+    if(NOT (CMAKE_SYSTEM_NAME STREQUAL "OpenBSD"))
+        if (NOT APPLE)
             # Error if there's symbols that are not found at link time.
             add_link_options("-Wl,--no-undefined")
         endif()
+    endif()
 elseif(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang" AND NOT MSVC)
     add_compile_options(-Wall -Wuninitialized -Wunused -Wunused-local-typedefs
                         -Wunused-parameter -Wunused-value  -Wunused-variable)
@@ -156,11 +158,9 @@ elseif(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang" AND NOT MSVC)
         add_compile_options(-fno-exceptions)
     endif()
 
-    if(NOT (CMAKE_SYSTEM_NAME STREQUAL "OpenBSD" OR CMAKE_SYSTEM_NAME STREQUAL "Emscripten"))
+    if(NOT (CMAKE_SYSTEM_NAME MATCHES "OpenBSD|Emscripten"))
         # Error if there's symbols that are not found at link time. Some linkers do not support this flag.
-        if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+        if(NOT APPLE)
-            add_link_options("-Wl,-undefined,error")
-        elseif(NOT APPLE)
             add_link_options("-Wl,--no-undefined")
         endif()
     endif()