Disable clang-tidy lint in C++ header body (#94)

Disable all clang-tidy linting in C++ the body of the C++ outline
template. This fixes several readability lint errors downstream.
diff --git a/compiler/back_end/cpp/generated_code_templates b/compiler/back_end/cpp/generated_code_templates
index 5ef58a5..4554b39 100644
--- a/compiler/back_end/cpp/generated_code_templates
+++ b/compiler/back_end/cpp/generated_code_templates
@@ -37,7 +37,9 @@
 
 $_includes_$
 
+// NOLINTBEGIN
 $_body_$
+// NOLINTEND
 
 #endif  // $_header_guard_$