build(node): add KOKORO_BUILD_ARTIFACTS_SUBDIR to env (#437)

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Source-Link: googleapis/synthtool@ba9918c

packages/google-cloud-dns/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-dns.git",
-        "sha": "3a82c8de942a93aeb4cf42f4c9f5170456fb4ebf"
+        "sha": "e1490bad130e35a3f0fbb4732d2a34fd220b5ec9"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "89c849ba5013e45e8fb688b138f33c2ec6083dc5"
+        "sha": "ba9918cd22874245b55734f57470c719b577e591"
       }
     }
   ],