Stops unplugging packages when the install scripts are disabled (#6820)

* Stops unplugging packages when the install scripts are disabled

* Update CHANGELOG.md

Author: arcanis

CHANGELOG.md

@@ -28,6 +28,10 @@ Please add one entry in this file for each change in Yarn's behavior. Use the sa
 
   [#6712](https://github.com/yarnpkg/yarn/pull/6712) - [**Maël Nison**](https://twitter.com/arcanis)
 
+- Stops automatically unplugging packages with postinstall script when running under `--ignore-scripts`
+
+  [#6820](https://github.com/yarnpkg/yarn/pull/6820) - [**Maël Nison**](https://twitter.com/arcanis)
+
 - Adds transparent support for the [`resolve`](https://github.com/browserify/resolve) package when using Plug'n'Play
 
   [#6816](https://github.com/yarnpkg/yarn/pull/6816) - [**Maël Nison**](https://twitter.com/arcanis)

src/package-linker.js

@@ -698,7 +698,11 @@ export default class PackageLinker {
     }
 
     // If the package has a postinstall script, we also unplug it (otherwise they would run into the cache)
-    if (pkg.scripts && (pkg.scripts.preinstall || pkg.scripts.install || pkg.scripts.postinstall)) {
+    if (
+      !this.config.ignoreScripts &&
+      pkg.scripts &&
+      (pkg.scripts.preinstall || pkg.scripts.install || pkg.scripts.postinstall)
+    ) {
       return true;
     }