[lld-macho][arm64] Enhance safe ICF with thunk-based deduplication (#106573)

Currently, our `safe` ICF mode only merges non-address-significant code,
leaving duplicate address-significant functions in the output. This
patch introduces `safe_thunks` ICF mode, which keeps a single master
copy of each function and replaces address-significant duplicates with
thunks that branch to the master copy.
Currently `--icf=safe_thunks` is only supported for `arm64`
architectures.

**Perf stats for a large binary:**
| ICF Option | Total Size | __text Size | __unwind_info | % total |

|-------------------|------------|-------------|---------------------|---------------------------|
| `--icf=none` | 91.738 MB | 55.220 MB | 1.424 MB | 0% |
| `--icf=safe` | 85.042 MB | 49.572 MB | 1.168 MB | 7.30% |
| `--icf=safe_thunks` | 84.650 MB | 49.219 MB | 1.143 MB | 7.72% |
| `--icf=all` | 82.060 MB | 48.726 MB | 1.111 MB | 10.55% |

So overall we can expect a `~0.45%` binary size reduction for a typical
large binary compared to the `--icf=safe` option.

**Runtime:**
Linking the above binary took ~10 seconds. Comparing the link
performance of --icf=safe_thunks vs --icf=safe, a ~2% slowdown was
observed.

1 files changed, 1 insertions, 1 deletions

diff --git a/lld/MachO/MapFile.cpp b/lld/MachO/MapFile.cpp
index 5bcaeca48da2..9c0621622ae2 100644
--- a/lld/MachO/MapFile.cpp
+++ b/lld/MachO/MapFile.cpp
@@ -156,7 +156,7 @@ static void printNonLazyPointerSection(raw_fd_ostream &os,
 }
 
 static uint64_t getSymSizeForMap(Defined *sym) {
-  if (sym->wasIdenticalCodeFolded)
+  if (sym->identicalCodeFoldingKind == Symbol::ICFFoldKind::Body)
     return 0;
   return sym->size;
 }