Tracking issue: WASM rmake test coverage for `#[export_visibility]`

This is a follow-up to https://github.com/rust-lang/rust/pull/151431#issuecomment-3923604898 which suggested to open a separate issue for discussing end-to-end, rmake-based wasm testing of #[export_visibility] and what would be necessary for that.

IIUC this requires:

• Enabling "wasm" crate feature of the object crate dependency in src/tools/run-make-support/Cargo.toml - something like: object = { version = "0.37", features = ["read", "compression", "wasm"] }
• Tweaking fn dynamic_lib_prefix and fn dynamic_lib_extension in src/tools/run-make-support/src/artifact_names.rs to use WASM-related values from library/std/src/sys/env_consts.rs
• Ensure that exported_dynamic_symbol_names works for wasm. It uses object::File::exports, which isn't implemented yet for wasm (as pointed out in https://github.com/rust-lang/rust/pull/151431#issuecomment-3919390374)

Start with src/tools/run-make-support/Cargo.toml, then inspect dynamic_lib_prefix and dynamic_lib_extension in src/tools/run-make-support/src/artifact_names.rs. Read how exported_dynamic_symbol_names uses object::File::exports and the linked discussions about WASM support. Done means the required end-to-end, rmake-based WASM coverage for #[export_visibility] is defined and the listed support gaps are addressed.