compiler_types: add comment on __BINDGEN__

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

include/linux/compiler_types.h

@@ -4,6 +4,10 @@
 
 #ifndef __ASSEMBLY__
 
+/*
+ * Skipped when running bindgen due to a libclang issue;
+ * see https://github.com/rust-lang/rust-bindgen/issues/2244.
+ */
 #if defined(CONFIG_DEBUG_INFO_BTF) && defined(CONFIG_PAHOLE_HAS_BTF_TAG) && \
 	__has_attribute(btf_type_tag) && !defined(__BINDGEN__)
 # define BTF_TYPE_TAG(value) __attribute__((btf_type_tag(#value)))