Fix aarch64 macOS crash when SIP disabled (JLJITLinkMemoryManager)

Apple ARM CPUs treat the `ic ivau` as a memory read, which causes a confusing
crash in DualMapAllocator if we try using it on a wr_addr that has been
mprotected to `Prot::NO`, since we are still holding the allocator lock.

For Apple aarch64 systems with SIP disabled, this will result in some memory
savings, since DualMapAllocator will now work there.  Like before, other JITLink
platforms, namely Linux aarch64 and RISC-V, will benefit too.

This re-lands #60105, after it was reverted in #60196.  Thanks @giordano!

Author: xal-0

src/cgmemmgr.cpp

@@ -548,13 +548,12 @@ class ROAllocator {
     virtual ~ROAllocator() JL_NOTSAFEPOINT {}
     virtual void finalize() JL_NOTSAFEPOINT
     {
-        for (auto &alloc: allocations) {
-            // ensure the mapped pages are consistent
-            sys::Memory::InvalidateInstructionCache(alloc.wr_addr,
-                                                    alloc.sz);
-            sys::Memory::InvalidateInstructionCache(alloc.rt_addr,
-                                                    alloc.sz);
-        }
+        // Note: on some aarch64 platforms, like Apple CPUs, we need read
+        // permission in order to invalidate instruction cache lines.  We are
+        // not guaranteed to have read permission on the wr_addr when using
+        // DualMapAllocator.
+        for (auto &alloc : allocations)
+            sys::Memory::InvalidateInstructionCache(alloc.rt_addr, alloc.sz);
         completed.clear();
         allocations.clear();
     }