I have the same issue (Unresolved import for platform specific modules) where rust-analyzer wrongly lints some imports. The solution is to disable that feature with:
"rust-analyzer.diagnostics.disabled": ["unresolved-import"]
How can I pass this config to Atom's ide-rust package?
I can't find any details in rust-analyzer documentation and VScode specific "setting.json" config file doesn't work in Atom case.