[release/10.0] Mark labels in x64 write barrier code as local/alt_entry (#120923)

Backport of #119245 to release/10.0

/cc @agocke @filipnavara

## Customer Impact

- [ ] Customer reported
- [X] Found internally

[Select one or both of the boxes. Describe how this issue impacts
customers, citing the expected and actual behaviors and scope of the
issue. If customer-reported, provide the issue number.]

## Regression

- [X] Yes
- [ ] No

This is a regression in the new Apple toolset.

## Testing

Tested manually, and in macios CI.

## Risk

Medium, product change coming somewhat late. However, this change has
been running in the `main` branch for a couple weeks with no issue.

---------

Co-authored-by: Filip Navara <[email protected]>

Author: github-actions[bot]

eng/native/configurecompiler.cmake

@@ -34,6 +34,13 @@ if (CLR_CMAKE_HOST_UNIX)
     endif()
 endif()
 
+# Force usage of classic linker on Xcode 15
+if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" AND
+    CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 15 AND
+    CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16)
+    add_link_options("-Wl,-ld_classic")
+endif()
+
 if (CMAKE_CONFIGURATION_TYPES) # multi-configuration generator?
     set(CMAKE_CONFIGURATION_TYPES "Debug;Checked;Release;RelWithDebInfo" CACHE STRING "" FORCE)
 endif (CMAKE_CONFIGURATION_TYPES)

src/coreclr/pal/inc/unixasmmacrosamd64.inc

@@ -53,8 +53,13 @@ C_FUNC(\Name):
 .endm
 
 .macro LEAF_END_MARKED Name, Section
-C_FUNC(\Name\()_End):
+#if defined(__APPLE__)
+        .alt_entry C_FUNC(\Name\()_End)
+        .private_extern C_FUNC(\Name\()_End)
+#else
         .global C_FUNC(\Name\()_End)
+#endif
+C_FUNC(\Name\()_End):
         LEAF_END \Name, \Section
         // make sure this symbol gets its own address
         nop

src/coreclr/pal/inc/unixasmmacrosarm64.inc

@@ -64,8 +64,13 @@ C_FUNC(\Name):
 .endm
 
 .macro LEAF_END_MARKED Name, Section
-C_FUNC(\Name\()_End):
+#if defined(__APPLE__)
+        .alt_entry C_FUNC(\Name\()_End)
+        .private_extern C_FUNC(\Name\()_End)
+#else
         .global C_FUNC(\Name\()_End)
+#endif
+C_FUNC(\Name\()_End):
         LEAF_END \Name, \Section
         // make sure this symbol gets its own address
         nop

src/coreclr/vm/amd64/CachedInterfaceDispatchCoreCLR.S

@@ -23,7 +23,7 @@ LEAF_ENTRY RhpVTableOffsetDispatch, _TEXT
         // to get the address in the vtable chunk list of what we want to dereference
 #ifdef TARGET_APPLE
 // Apple's linker has issues which break unwind info if
-// an ALTERNATE_ENTRY is present in the middle of a function see https://github.com/dotnet/runtime/pull/114982#discussion_r2083272768
+// an ALTERNATE_ENTRY is present in the middle of a function see https://github.com/dotnet/runtime/issues/119005
 .cfi_endproc
 #endif
     ALTERNATE_ENTRY RhpVTableOffsetDispatchAVLocation