gyp: fix v8 canary build on aix

PR-URL: #45496
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Ujjwal Sharma <ryzokuken@disroot.org>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

tools/v8_gypfiles/toolchain.gypi

@@ -1125,7 +1125,7 @@
             'ldflags': [ '-Wl,-bmaxdata:0x60000000/dsa' ],
           }],
           [ 'v8_target_arch=="ppc64"', {
-            'cflags': [ '-maix64', '-fdollars-in-identifiers' ],
+            'cflags': [ '-maix64', '-fdollars-in-identifiers', '-fno-extern-tls-init' ],
             'ldflags': [ '-maix64 -Wl,-bbigtoc' ],
           }],
         ],