limit to apple only

src/CMakeLists.txt

@@ -139,7 +139,6 @@ else()
         -Wno-invalid-offsetof
         -Wno-unused-parameter
         -Wno-missing-field-initializers
-        -Wno-unused-private-field
     )
 
     if (CXX_CLANG OR CXX_ICC) # Clang or AppleClang
@@ -166,6 +165,10 @@ else()
         add_compile_options("-stdlib=libc++")
     endif()
 
+    if (CXX_APPLE)
+        add_compile_options(-Wno-unused-private-field)
+    endif()
+
     # GCC bugs
     if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "11" AND CXX_GCC)
         # These diagnostics would be great if they worked, but are just completely broken