Fix rollup config for compatibility layer builds (#5664)

* Fix rollup config for compat

* Add changeset

* Formatting

Author: sam-gc

.changeset/selfish-tools-obey.md

@@ -0,0 +1,5 @@
+---
+"firebase": patch
+---
+
+Fix compatability layer errors that were being thrown in Safari

packages/firebase/compat/rollup.config.js

@@ -29,6 +29,10 @@ import compatPkg from './package.json';
 import appPkg from './app/package.json';
 
 const external = Object.keys(pkg.dependencies || {});
+const uglifyOptions = {
+  mangle: true,
+  webkit: true // Necessary to avoid https://bugs.webkit.org/show_bug.cgi?id=223533
+};
 
 /**
  * Global UMD Build
@@ -123,7 +127,7 @@ const appBuilds = [
       format: 'umd',
       name: GLOBAL_NAME
     },
-    plugins: [...plugins, typescriptPluginCDN, uglify()]
+    plugins: [...plugins, typescriptPluginCDN, uglify(uglifyOptions)]
   }
 ];
 
@@ -163,7 +167,7 @@ const componentBuilds = compatPkg.components
       {
         input: `${__dirname}/${component}/index.ts`,
         output: createUmdOutputConfig(`firebase-${component}-compat.js`),
-        plugins: [...plugins, typescriptPluginCDN, uglify()],
+        plugins: [...plugins, typescriptPluginCDN, uglify(uglifyOptions)],
         external: ['@firebase/app-compat', '@firebase/app']
       }
     ];
@@ -197,7 +201,7 @@ const completeBuilds = [
       sourcemap: true,
       name: GLOBAL_NAME
     },
-    plugins: [...plugins, typescriptPluginCDN, uglify()]
+    plugins: [...plugins, typescriptPluginCDN, uglify(uglifyOptions)]
   },
   /**
    * App Node.js Builds
@@ -244,7 +248,7 @@ const completeBuilds = [
       typescriptPluginCDN,
       json(),
       commonjs(),
-      uglify()
+      uglify(uglifyOptions)
     ]
   },
   /**