Windows build and dev support for kit package

[ryc76]

pnpm build and dev commands were failing on Windows due to lack of "rm" command as specified in packages\kit\package.json

"dev": "rm -rf assets/runtime && rollup -cw",
"build": "rm -rf assets/runtime && rollup -c",

Have added run-script-os NPM package to allow OS dependant commands to run and added equivalent Windows command

"build": "run-script-os",
"dev": "run-script-os",
"dev:default": "rm -rf assets/runtime && rollup -cw",
"dev:win32": "del /S /Q assets\runtime && rollup -cw",
"build:default": "rm -rf assets/runtime && rollup -c",
"build:win32": "del /S /Q assets\runtime && rollup -c",

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• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

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[benmccann]

Thanks for this. We'd probably like to avoid adding any new dependencies and just call node -e "whatever" instead using fs.rm / fs.rmdir or whatever

[benmccann]

Or just call those commands synchronously at the top of rollup.config.js

[Conduitry]

So, something like:

diff --git a/packages/kit/package.json b/packages/kit/package.json
index 0b7fa33..0d1ffe4 100644
--- a/packages/kit/package.json
+++ b/packages/kit/package.json
@@ -49,8 +49,8 @@
 		"svelte-kit.js"
 	],
 	"scripts": {
-		"dev": "rm -rf assets/runtime && rollup -cw",
-		"build": "rm -rf assets/runtime && rollup -c",
+		"dev": "rollup -cw",
+		"build": "rollup -c",
 		"lint": "eslint --ignore-path .gitignore \"src/**/*.{ts,mjs,js,svelte}\" && npm run check-format",
 		"check": "tsc && svelte-check",
 		"format": "prettier --write . --config ../../.prettierrc --ignore-path .gitignore",
diff --git a/packages/kit/rollup.config.js b/packages/kit/rollup.config.js
index 9d1e936..8a2fca1 100644
--- a/packages/kit/rollup.config.js
+++ b/packages/kit/rollup.config.js
@@ -1,3 +1,6 @@
+import fs from 'fs';
+(fs.rmSync || fs.rmdirSync)('assets/runtime', { recursive: true, force: true });
+
 import commonjs from '@rollup/plugin-commonjs';
 import replace from '@rollup/plugin-replace';
 import resolve from '@rollup/plugin-node-resolve';