fix: use correct escaping in the context of regex (#6449)

Author: comawill

bin/build-tools/lib/build-windows.ts

@@ -63,7 +63,7 @@ export async function buildWindowsConfig(
     ignore: [
       new RegExp(`${commonConfig.electronDirectory}/renderer/src$`),
       new RegExp(`${commonConfig.electronDirectory}/src$`),
-      new RegExp(`/\.yarn$`),
+      new RegExp(`/\\.yarn$`),
       new RegExp(`/bin$`),
       new RegExp(`/jenkins$`),
     ],