File gitignore.patch of Package waterfox-classic-kpe

diff --git a/third_party/rust/packed_simd_2/perf-guide/.gitignore b/third_party/rust/packed_simd_2/perf-guide/.gitignore
new file mode 100644
index 000000000000..5a0bf0317d75
--- /dev/null
+++ b/third_party/rust/packed_simd_2/perf-guide/.gitignore
@@ -0,0 +1 @@
+/book