refactor: fix/simplify proto gen scripts (#542)

package.json

@@ -44,10 +44,9 @@
     "compile": "tsc -p . && cp -r src/v1 build/src/ && cp -r protos build/ && cp -r proto build/ && cp smoke-test/*.js build/system-test && cp test/*.js build/test",
     "prepare": "npm run compile",
     "pretest": "npm run compile",
-    "proto": "npm run proto:pubsub",
-    "proto:pubsub": "pbjs -t static-module -w commonjs -p protos google/pubsub/v1/pubsub.proto | pbts -i long -o proto/pubsub.d.ts -",
-    "proto:iam": "pbjs -t static-module -w commonjs -p protos google/iam/v1/iam_policy.proto | pbts -i long -o proto/iam.d.ts -",
-    "proto-types": "mkdir -p proto && npm run proto:pubsub && npm run proto:iam",
+    "proto": "mkdirp proto && npm run proto:pubsub && npm run proto:iam",
+    "proto:pubsub": "pbjs -t static-module -w commonjs -p protos google/pubsub/v1/pubsub.proto | pbts -o proto/pubsub.d.ts -",
+    "proto:iam": "pbjs -t static-module -w commonjs -p protos google/iam/v1/iam_policy.proto | pbts -o proto/iam.d.ts -",
     "docs-test": "linkinator docs -r --skip www.googleapis.com",
     "predocs-test": "npm run docs"
   },
@@ -92,6 +91,7 @@
     "jsdoc": "^3.5.5",
     "jsdoc-baseline": "git+https://github.com/hegemonic/jsdoc-baseline.git",
     "linkinator": "^1.1.2",
+    "mkdirp": "^0.5.1",
     "mocha": "^6.0.0",
     "mv": "^2.1.1",
     "ncp": "^2.0.0",