Clean check in prepublishOnly (#9590)

* Clean check in prepublishOnly

Runs clean check as a first step in prepublishOnly.
This ensures a clean directory before building the build content and
before the manual diffing with previously published tarball.

* Address comments

package.json

@@ -127,7 +127,7 @@
     "build-prod-min": "rollup -c --environment BUILD:production,MINIFY:true",
     "build-csp": "rollup -c rollup.config.csp.js",
     "build-query-suite": "rollup -c test/integration/rollup.config.test.js",
-    "build-flow-types": "cp build/mapbox-gl.js.flow dist/mapbox-gl.js.flow && cp build/mapbox-gl.js.flow dist/mapbox-gl-dev.js.flow",
+    "build-flow-types": "mkdir -p dist && cp build/mapbox-gl.js.flow dist/mapbox-gl.js.flow && cp build/mapbox-gl.js.flow dist/mapbox-gl-dev.js.flow",
     "build-css": "postcss -o dist/mapbox-gl.css src/css/mapbox-gl.css",
     "build-style-spec": "cd src/style-spec && npm run build && cd ../.. && mkdir -p dist/style-spec && cp src/style-spec/dist/* dist/style-spec",
     "watch-css": "postcss --watch -o dist/mapbox-gl.css src/css/mapbox-gl.css",
@@ -141,6 +141,7 @@
     "start-bench": "run-p build-token watch-benchmarks start-server",
     "start-release": "run-s build-token build-prod-min build-css print-release-url start-server",
     "diff-tarball": "build/run-node build/diff-tarball && echo \"Please confirm the above is correct [y/n]? \"; read answer; if [ \"$answer\" = \"${answer#[Yy]}\" ]; then false; fi",
+    "prepare-publish": "git clean -fdx && yarn install",
     "lint": "eslint --cache --ignore-path .gitignore src test bench debug/*.html",
     "lint-docs": "documentation lint src/index.js",
     "lint-css": "stylelint 'src/css/mapbox-gl.css'",
@@ -157,7 +158,7 @@
     "test-expressions": "build/run-node test/expression.test.js",
     "test-flow": "build/run-node build/generate-flow-typed-style-spec && flow .",
     "test-cov": "nyc --require=@mapbox/flow-remove-types/register --reporter=text-summary --reporter=lcov --cache run-s test-unit test-expressions test-query test-render",
-    "prepublishOnly": "run-s build-flow-types build-dev build-prod-min build-prod build-csp build-css build-style-spec test-build diff-tarball",
+    "prepublishOnly": "run-s prepare-publish build-flow-types build-dev build-prod-min build-prod build-csp build-css build-style-spec test-build diff-tarball",
     "print-release-url": "node build/print-release-url.js",
     "codegen": "build/run-node build/generate-style-code.js && build/run-node build/generate-struct-arrays.js"
   },

src/style-spec/package.json

@@ -14,7 +14,7 @@
   "scripts": {
     "copy-flow-typed": "cp -R ../../flow-typed .",
     "build": "../../node_modules/.bin/rollup -c && ../../node_modules/.bin/rollup -c --environment esm",
-    "prepublish": "yarn copy-flow-typed && yarn build",
+    "prepublish": "git clean -fdx && yarn copy-flow-typed && yarn build",
     "postpublish": "rm -r flow-typed dist/index.js"
   },
   "repository": {