Check RUSTFLAGS for a linker before going to the cargo configs
Check RUSTFLAGS for a linker before going to the cargo configs

The splitting of RUSTFLAGS into tokens is ripped from Cargo so it should work
exactly as it does.

Signed-off-by: Gabriel Smith <81bf9ba0f03e0524e8363ab0b55760deec97bc99@gmail.com>

xd009642/tarpaulin,xd009642/tarpaulin