Probably a dumb question, but I'd really like to know if this somehow affects/improves Rust's support for dynamic linking in any way (i.e., when comiling Rust code with the GCC-based toolchain, instead of with rustc)?
I would naively assume that it doesn't affect it at all. Compiling with GCC doesn't magically make dynamic linking better. The limitation in dynamic linking is an element of language design.
I'd also note that any Rust you compile with GCC probably shouldn't be dynamically linked with Rust code compiled with rustc.
I'd also note that any Rust you compile with GCC probably shouldn't be dynamically linked with Rust code compiled with rustc.