This target covers MIPS devices that run the trunk version of OpenWRT.

The x86_64-unknown-linux-musl target always links statically to C libraries. For
the mips(el)-unknown-linux-musl target, we opt for dynamic linking (like most of
other targets do) to keep binary size down.

As for the C compiler flags used in the build system, we use the same flags used
for the mips(el)-unknown-linux-gnu target.

cf rust-lang#31303

fixes failed test (std::os::raw::tests::unix) in x86_64-musl target