win/openssl: mark assembled object files as seh safe

There are no unsafe structured exception handlers in object files
generated from hand-crafted assembly - because they contain no exception
handlers at all.

deps/openssl/openssl.gyp

@@ -824,6 +824,7 @@
                   'action': [
                     'ml.exe',
                     '/Zi',
+                    '/safeseh',
                     '/Fo', '<(INTERMEDIATE_DIR)/<(RULE_INPUT_ROOT).obj',
                     '/c', '<(RULE_INPUT_PATH)',
                   ],