Fix PAL_DispatchException linker error

Seemingly only needed for macOS. Linker complains about references to it
under some configurations.

pal/src/CMakeLists.txt

@@ -71,8 +71,12 @@ if(CC_TARGETS_AMD64 OR CC_TARGETS_X86)
     arch/i386/asmhelpers.S
     )
 elseif(PAL_CMAKE_PLATFORM_ARCH_ARM64)
+  if(CC_TARGET_OS_OSX)
+    set(PLATFORM_SOURCES ${PLATFORM_SOURCES}
+      arch/arm64/dispatchexceptionwrapper.S
+    )
+  endif()
   set(ARCH_SOURCES
-    arch/arm64/dispatchexceptionwrapper.S
     arch/arm64/context2.S
     arch/arm64/debugbreak.S
   )