build: disable ICF for mksnapshot

Refs: https://chromium-review.googlesource.com/c/v8/v8/+/5447267
Co-authored-by: Michaël Zasso <targos@protonmail.com>

Author: LeszekSwirski

node.gyp

@@ -1376,6 +1376,12 @@
         'tools/snapshot/node_mksnapshot.cc',
       ],
 
+      'msvs_settings': {
+        'VCLinkerTool': {
+          'EnableCOMDATFolding': '1', # /OPT:NOICF
+        },
+      },
+
       'conditions': [
         ['node_write_snapshot_as_array_literals=="true"', {
           'defines': [ 'NODE_MKSNAPSHOT_USE_ARRAY_LITERALS=1' ],

tools/v8_gypfiles/v8.gyp

@@ -1708,6 +1708,24 @@
       'sources': [
         '<!@pymod_do_main(GN-scraper "<(V8_ROOT)/BUILD.gn"  "\\"mksnapshot.*?sources = ")',
       ],
+      'configurations': {
+        # We have to repeat the settings for each configuration because toochain.gypi
+        # defines the default EnableCOMDATFolding value in the configurations dicts.
+        'Debug': {
+          'msvs_settings': {
+            'VCLinkerTool': {
+              'EnableCOMDATFolding': '1', # /OPT:NOICF
+            },
+          },
+        },
+        'Release': {
+          'msvs_settings': {
+            'VCLinkerTool': {
+              'EnableCOMDATFolding': '1', # /OPT:NOICF
+            },
+          },
+        },
+      },
       'conditions': [
         ['want_separate_host_toolset', {
           'toolsets': ['host'],

unofficial.gni

@@ -234,13 +234,30 @@ template("node_gn_build") {
   if (node_use_node_snapshot) {
     if (current_toolchain == v8_snapshot_toolchain) {
       executable("node_mksnapshot") {
-        configs += [ ":node_internal_config" ]
+        configs += [ ":node_internal_config", ":disable_icf" ]
         sources = [
           "src/node_snapshot_stub.cc",
           "tools/snapshot/node_mksnapshot.cc",
         ]
         deps = [ ":libnode" ]
       }
+
+      # This config disables a link time optimization "ICF", which may merge
+      # different functions into one if the function signature and body of them are
+      # identical.
+      #
+      # ICF breaks 1:1 mappings of the external references for V8 snapshot, so we
+      # disable it while taking a V8 snapshot.
+      config("disable_icf") {
+        visibility = [ ":*" ]  # Only targets in this file can depend on this.
+        if (is_win) {
+          ldflags = [ "/OPT:NOICF" ]  # link.exe, but also lld-link.exe.
+        } else if (is_apple && !use_lld) {
+          ldflags = [ "-Wl,-no_deduplicate" ]  # ld64.
+        } else if (use_gold || use_lld) {
+          ldflags = [ "-Wl,--icf=none" ]
+        }
+      }
     }
 
     action("run_node_mksnapshot") {