Found staticlib .. instead of rlib or dylib.
Consider the following two files:
a.rs
#![crate_type = "staticlib"] fn foo() {}
main.rs
extern crate a; fn main() { a::foo(); }
Crate a is compiled as a staticlib. A staticlib is a system-dependant library only intended for linking with non-Rust applications (C programs). Note that staticlibs include all upstream dependencies (core, std, other user dependencies, etc) which makes them significantly larger than dylibs: prefer staticlib for linking with C programs. Learn more about different crate_types in this section of the Reference.
This error can be fixed by:
rlib or dylib; formats suitable for Rust linking.