README.md: Command line example does not work with rustc nightly 2020-04-30 #427
Description
The following command line option no longer works with rustc nightly due to the removal of the -Zno-landing-pads option (rust-lang/rust#70175)
export CARGO_INCREMENTAL=0
export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zno-landing-pads"