packages/cli: make plugin build generate usable declaration maps

packages/cli/src/commands/plugin/rollup.config.ts

@@ -50,6 +50,12 @@ export default {
         // The dev folder is for the local plugin serve, ignore it in the build
         // If we don't do this we get a folder structure similar to dist/{src,dev}/...
         exclude: ['dev'],
+        compilerOptions: {
+          // Use absolute path to src dir as root for declarations, relying on the default
+          // seems to produce declaration maps that are relative to dist/ instead of src/
+          // Using a relative path like ../src doesn't work either becaus it will be used as is in subdirs.
+          sourceRoot: paths.resolveTarget('src'),
+        },
       },
       clean: true,
     }),