tools: add missing highway defines for IBM i

This was added for AIX but should have included IBM i as well.

PR-URL: https://github.com/nodejs/node/pull/58335
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>

tools/v8_gypfiles/v8.gyp

@@ -2291,7 +2291,7 @@
           ['v8_target_arch=="s390x"', {
             'defines': ['HWY_BROKEN_EMU128=0',],
           }],
-          ['OS == "aix"', {
+          ['OS in "aix os400"', {
             'defines': ['HWY_BROKEN_EMU128=0',],
           }],
           ['v8_target_arch=="arm" and arm_version==7', {