gccrs: fix segfault on exported macro

gccrs: fix segfault on exported macro

An imbricated exported macro leads to a segfault.

gcc/rust/ChangeLog:

	* metadata/rust-export-metadata.cc (ExportContext::emit_macro):
	Change method argument NodeId to AST::MacroRulesDefinition.
	* metadata/rust-export-metadata.h:
	Likewise.
	* util/rust-hir-map.cc (Mappings::insert_exported_macro):
	Insert AST::MacroRulesDefinition instead of NodeId.
	* util/rust-hir-map.h:
	Change methods declarations of exported macros.

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3617.rs: New test.

Signed-off-by: Lucas Ly Ba <lucas.ly-ba@outlook.fr>