build: fix what the sixth node.yml run found

win32 got past the ICU object the fifth run fixed - genccode now writes it as
IMAGE_FILE_MACHINE_I386, and the log confirms it: "genccode: using architecture
cpu=332 bits=32 big-endian=0". Then the linker refused the object it had just
been taught to write:

  lld-link : error : /safeseh: ../obj/global_intermediate/icudt78l_dat.obj is
  not compatible with SEH [tools\v8_gypfiles\gen-regexp-special-case.vcxproj]

icudt78l_dat.obj is generated DATA. It holds no code, so it has no safe
exception handler table and nothing can give it one; opting out of /SAFESEH is
the only way to link it. That is not a new discovery - node.gyp already carried
ImageHasSafeExceptionHandlers: 'false', restored with 32-bit Windows and
originally from nodejs#25852.

It was in the wrong place. A target_defaults in node.gyp reaches only the
targets NODE.GYP DEFINES, and this object is linked by targets in
tools/v8_gypfiles/v8.gyp and tools/icu/icu-generic.gyp - gen-regexp-special-case
is one of V8's build tools - which never saw the setting. Nothing had to opt
those in before because gyp turns /SAFESEH on BY ITSELF for every x86 link
(safeseh_default = "true" when the arch is x86, in
tools/gyp/pylib/gyp/msvs_emulation.py), and upstream stopped building the one
architecture where that default means anything.

The opt-out moves to common.gypi, scoped to ia32 - the only architecture
/SAFESEH applies to, which the node.gyp copy was not. tools/gyp_node.py passes
common.gypi to gyp with -I, and LoadTargetBuildFile passes its includes down to
every dependency build file it loads (tools/gyp/pylib/gyp/input.py), so one rule
there covers node, V8 and ICU alike.

NOT verified: the build itself, which needs a Windows runner - there is none
here, and the other five jobs of the sixth run are still going, so only win32's
log exists to read. What was checked: that common.gypi and node.gyp are still
valid gyp literals and the ia32 linker condition now reads {'TargetMachine': 1,
'ImageHasSafeExceptionHandlers': 'false'}; that the vendored gyp converts that
to the MSBuild Link setting with no validation errors, which is what MSBuild
turns into /SAFESEH:NO; that gyp really does default /SAFESEH on for x86; and
that gyp really does hand -I includes down to dependency build files, which is
the whole reason common.gypi is the right place for it.

Thanks to xet7 !

Author: xet7

common.gypi

@@ -402,6 +402,32 @@
         'conditions': [
           ['target_arch=="ia32"', {
             'TargetMachine' : 1,              # /MACHINE:X86
+            # /SAFESEH:NO, and it has to be HERE rather than in node.gyp.
+            #
+            # gyp turns /SAFESEH on by ITSELF for every x86 link -
+            # tools/gyp/pylib/gyp/msvs_emulation.py sets
+            # safeseh_default = "true" when the arch is x86 - so opting out is
+            # not a preference, it is the only way to link an object that
+            # carries no safe-exception-handler table. ICU's genccode writes
+            # exactly such an object: icudt<ver>l_dat.obj is generated data
+            # with no code and no SEH table in it, and the sixth workflow run
+            # died on it - "lld-link : error : /safeseh:
+            # ../obj/global_intermediate/icudt78l_dat.obj is not compatible
+            # with SEH" - while linking gen-regexp-special-case, one of V8's
+            # build tools.
+            #
+            # node.gyp already carried this setting, restored with 32-bit
+            # Windows, but a target_defaults in node.gyp reaches only the
+            # targets node.gyp DEFINES. The object is linked by targets in
+            # tools/v8_gypfiles/v8.gyp and tools/icu/icu-generic.gyp, which
+            # never saw it. common.gypi is included into every .gyp in the tree
+            # (tools/gyp_node.py passes it with -I), so one rule here covers
+            # node, V8 and ICU alike - and it is scoped to ia32, which is the
+            # only architecture /SAFESEH means anything on.
+            #
+            # Refs: https://github.com/nodejs/node/pull/25852 and
+            # https://docs.microsoft.com/en-us/cpp/build/reference/safeseh-image-has-safe-exception-handlers
+            'ImageHasSafeExceptionHandlers': 'false',
           }],
           ['target_arch=="x64"', {
             'TargetMachine' : 17,             # /MACHINE:X64

node.gyp

@@ -548,14 +548,10 @@
         'libraries': ['-latomic'],
       }],
     ],
-    # Relevant only for x86, restored with 32-bit Windows (removed upstream in
-    # 7ad0cc3e571). Refs: https://github.com/nodejs/node/pull/25852 and
-    # https://docs.microsoft.com/en-us/cpp/build/reference/safeseh-image-has-safe-exception-handlers
-    'msvs_settings': {
-      'VCLinkerTool': {
-        'ImageHasSafeExceptionHandlers': 'false',
-      },
-    },
+    # The x86 /SAFESEH:NO opt-out that used to sit here - restored with 32-bit
+    # Windows, removed upstream in 7ad0cc3e571 - moved to common.gypi, where it
+    # reaches V8's and ICU's targets as well as node's own. See the comment
+    # there for what it is for and why it has to be global.
   },
 
   'targets': [