Don't tidy/format files in subproject

This pattern and files are copied from bmcweb.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: If048cbd458bb7e1bcf704daf60cf060af359ef81
diff --git a/subprojects/.clang-tidy b/subprojects/.clang-tidy
new file mode 100644
index 0000000..612bd0e
--- /dev/null
+++ b/subprojects/.clang-tidy
@@ -0,0 +1 @@
+Checks: '-*'