Treat perfetto_config.descriptor.h as binary.

This is so it does not spam our diffs.

Change-Id: Ia24871b5c8789bc0fd2de96a155be90162d18825
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..c77d717
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+src/perfetto_cmd/perfetto_config.descriptor.h binary